Update the README (#365)

This PR updates the README.md to be more user-friendly. The PR:
- adds description of project
- reframes documentation section into getting started for user and
developer personas
- adds explicit installation instructions for npe2 for pip and conda
- updates the CLI commands and examples
- adds a license section
- moves the historical content to the end
- adds Contact us section

I was trying to understand the technical architecture of the plugin
engine and created this to help me with my own understanding. Thought it
might be helpful for others too.

Closes #263.

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Peter Sobolewski <[email protected]>
Co-authored-by: Draga Doncila Pop <[email protected]>

README.md

@@ -1,41 +1,144 @@
-# npe2
+# npe2 - napari plugin engine version 2
 
 [![CI](https://github.com/napari/npe2/actions/workflows/ci.yml/badge.svg)](https://github.com/napari/npe2/actions/workflows/ci.yml)
 [![codecov](https://codecov.io/gh/napari/npe2/branch/main/graph/badge.svg?token=FTH635x542)](https://codecov.io/gh/napari/npe2)
 
-napari plugin refactor
+## Project description
 
-see also https://github.com/napari/napari/issues/3115
+The **napari plugin engine version 2**, **npe2** extends the functionality of
+[napari's core](https://github.com/napari/napari).
+The plugin ecosystem offers user additional functionality for napari as well
+as specific support for different scientific domains.
 
-## Documentation
+This repo contains all source code and documentation required for defining, validating and managing plugins for napari.
 
-For documentation on authoring npe2 plugins, see the [napari plugin docs](https://napari.org/stable/plugins/index.html).  These include:
-- the [manifest reference](https://napari.org/stable/plugins/technical_references/manifest.html)
-- the [contribution guide](https://napari.org/stable/plugins/building_a_plugin/guides.html)
+## Getting started
 
-## Command line tool
+The [napari plugin docs landing page](https://napari.org/stable/plugins/index.html)
+offers comprehensive information for **plugin users** and for **plugin developers**.
+
+### Plugin users
+
+For plugin users, the docs include information about:
+- [Starting to use plugins](https://napari.org/stable/plugins/start_using_plugins/index.html#plugins-getting-started)
+- [Finding and installing plugins](https://napari.org/stable/plugins/start_using_plugins/finding_and_installing_plugins.html#find-and-install-plugins)
+
+### Plugin developers
+
+For plugin developers, the docs cover topics like:
+- [Building a plugin](https://napari.org/stable/plugins/building_a_plugin/index.html)
+- [Guides to different plugin contributions](https://napari.org/stable/plugins/building_a_plugin/guides.html)
+- [Technical references such as the plugin manifest](https://napari.org/stable/plugins/technical_references/manifest.html)
+
+Try the [**napari plugin template**](https://github.com/napari/napari-plugin-template)
+to streamline development of a new plugin.
+
+## Installation
+
+The `npe2` command line tool can be installed with `pip` or `conda`, but will already be installed as a dependency if you have napari installed.
+
+### Using pip
+
+1. Create and activate a virtual environment.
+
+*If you are new to using virtual environments, visit our [virtual environments guide](https://napari.org/stable/plugins/virtual_environment_docs/1-virtual-environments.html)*.
+
+    ```bash
+    python3 -m venv .venv
+    source .venv/bin/activate
+    ```
+
+2. Install npe2.
+
+    ```bash
+    pip install npe2
+    ```
+
+3. Test your installation.
+
+    ```bash
+    npe2 --help
+    ```
+
+### Using conda
+
+1. Create and activate a virtual environment.
+
+    ```bash
+    conda create -n npe-test -c conda-forge python=3.12
+    conda activate npe-test
+    ```
+
+2. Install npe2.
+
+    ```bash
+    conda install npe2
+    ```
+
+3. Test your installation.
+
+    ```bash
+    npe2 --help
+    ```
+
+## Usage
+
+The command line tool `npe2` offers the following commands:
+
+```bash
+cache      Cache utils
+compile    Compile @npe2.implements contributions to generate a manifest.
+convert    Convert first generation napari plugin to new (manifest) format.
+fetch      Fetch manifest from remote package.
+list       List currently installed plugins.
+parse      Show parsed manifest as yaml.
+validate   Validate manifest for a distribution name or manifest filepath.
+```
+
+### Examples
+
+List currently installed plugins:
+
+```bash
+npe2 list
+```
+
+Compile a source directory to create a plugin manifest:
 
-Includes a command line tool `npe2` with the following commands:
 ```bash
-Commands:
-  cache     Cache utils
-  convert   Convert first generation napari plugin to new (manifest) format.
-  parse     Show parsed manifest as yaml
-  validate  Validate manifest for a distribution name or manifest filepath.
+npe2 compile PATH_TO_SOURCE_DIRECTORY
 ```
 
-examples:
+Convert current directory to an npe2-ready plugin
+(note: the repo must also be installed and importable in the current environment.):
 
 ```bash
-# convert current directory to an npe2-ready plugin
-# (note: the repo must also be installed and importable in the current environment)
 npe2 convert .
 ```
 
+Validate a plugin package. For example, a plugin named `your-plugin-package`:
+
 ```bash
 npe2 validate your-plugin-package
 ```
 
+Show a parsed manifest of your plugin:
+
 ```bash
 npe2 parse your-plugin-package
 ```
+
+## License
+
+npe2 uses the [BSD License](./LICENSE).
+
+## History
+
+This repo replaces the initial napari plugin engine v1.
+See also https://github.com/napari/napari/issues/3115 for
+motivation and technical discussion about the creation of v2.
+
+## Contact us
+
+Visit [our community documentation](https://napari.org/stable/community/index.html)
+or [open a new issue on this repo](https://github.com/napari/npe2/issues/new).