Merge branch 'develop' into feat/910-auto-linking-mention-from-html-t…

…o-markdown

README.md

@@ -446,6 +446,19 @@ var showdown    = require('showdown'),
     converter = new showdown.Converter({ extensions: ['myExtension'] });
 ```
 
+## Building
+
+Building your clone of the repository is easy.
+> Prerequesites: [Node.js](https://nodejs.org/) v12, [npm](https://www.npmjs.com/package/npm) and [npx](https://www.npmjs.com/package/npx) must be installed.
+
+1. run `npm install`.
+2. run `npx grunt build` (see [`Gruntfile.js`](/Gruntfile.js)). This command:
+
+    1. Cleans the repo.
+    2. Checks code quality ([JSHint](https://jshint.com/) and [ESLint](https://eslint.org/)).
+    3. Runs tests.
+    4. Creates the [distributable](/showdown.js) and [minified](/showdown.min.js) files in the [`dist`](/dist) folder.
+
 ## Tests
 
 A suite of tests is available which require Node.js.  Once Node is installed, run the following command from

docs/cli.md

@@ -150,4 +150,22 @@ showdown makehtml [options]
 
         ```sh
         showdown makehtml -e ~/twitter.js -e ~/youtube.js
-        ```
+        ```
+
+## Extra options
+
+You can specify any of the [supported options](available-options.md), and they will be passed to the converter.
+For example, you can enable strikethrough support via the following command:
+
+```
+showdown makehtml -i foo.md -o bar.html --strikethrough
+```
+
+this command is equivalent of doing:
+
+```js
+var conv = new showdown.Converter({strikethrough: true});
+```
+
+!!! warning ""
+    In the CLI tool, all the extra options are **disabled** by default. This is the opposite of what is defined for node and browser, where some options, like `ghCodeBlocks` are enabled (for backward compatibility and historical reasons).

docs/extensions-list.md

@@ -0,0 +1,24 @@
+## Official
+
+* [twitter-extension][1] - Adds support of Twitter usernames and hastags
+* [prettify-extension][2] - Adds [Google Prettify][3] hints to HTML output
+
+## Community
+
+* [showdown-icon][4] - Adds support of Glyphicon and font-awesome into Markdown
+* [showdown-xss-filter][5] - Filters XSS, using leizongmin/js-xss
+* [showdown-toc][6] - Adds Table of Contents
+* [showdown-footnotes][7] - Adds simple footnotes
+* [katex-latex][8] - Displays math using KaTeX and LaTeX or AsciiMath
+
+!!! note ""
+    If you have a Showdown extension you would like to add here, you can [raise an issue](https://github.com/showdownjs/showdown/issues).
+
+[1]: https://github.com/showdownjs/twitter-extension
+[2]: https://github.com/showdownjs/prettify-extension
+[3]: https://github.com/googlearchive/code-prettify
+[4]: https://github.com/dbtek/showdown-icon
+[5]: https://github.com/VisionistInc/showdown-xss-filter
+[6]: https://github.com/ravisorg/showdown-toc
+[7]: https://github.com/Kriegslustig/showdown-footnotes
+[8]: https://obedm503.github.io/showdown-katex