chore: add contributor guide

CONTRIBUTING.md

@@ -0,0 +1,32 @@
+# Contributor Guide
+
+## Getting started
+
+Make sure you have the Grit CLI installed:
+
+```sh
+npm install -g @getgrit/launcher
+```
+
+To propose changes, fork this repository and open a pull request.
+
+## Adding a new pattern
+
+All patterns require at least one sample validating the functionality. As a result, the best way to develop a
+GritQL pattern is often by starting with before and after sample(s) of the code to be transformed. You can
+iterate in the [GritQL studio](https://app.grit.io/studio) to develop your pattern.
+
+Once you have a pattern, you can add it to the repository by creating a new `.md` file in the `.grit/patterns`
+directory. The file name should be the snake-cased name of the pattern. Keep the file name short and
+descriptive, and add a concise description as well as any relevant tags. All PRs must contain at least
+one sample of before/after code with a descriptive name.
+
+## Testing
+
+Samples can be tested locally using the Grit CLI.
+
+```sh
+grit patterns test
+```
+
+Once you have your sample(s) passing locally, creating a PR will automatically trigger a CI build running the same tests in a range of environments.

README.md

@@ -0,0 +1,12 @@
+# JSON Grit Patterns
+
+This repository contains curated Grit patterns for JSON.
+
+## License
+
+This repository is licensed exclusively for usage with the Grit tool.
+All rights reserved.
+
+## Contributing
+
+We welcome contributions from the community. Please see the [contributing guide](CONTRIBUTING.md) for more information.