docs(v2): refactor docs for better outline and welcoming PRs (#1641)

* docs(v2): refactor docs for better outline and welcoming PRs

* docs(v2): update docs

website/docs/plugins-api.md

@@ -1,125 +0,0 @@
----
-id: plugins-api
-title: Plugins
----
-
-Plugins are one of the best ways to add functionality to our Docusaurus. Plugins allow third-party developers to extend or modify the default functionality that Docusaurus provides.
-
-## Installing a Plugin
-
-A plugin is usually a dependency, so you install them like other packages in node using NPM.
-
-```bash
-yarn add docusaurus-plugin-name
-```
-
-Then you add it in your site's `docusaurus.config.js` plugin arrays:
-
-```jsx
-module.exports = {
-  plugins: [
-    '@docusaurus/plugin-content-pages',
-    [
-      // Plugin with options
-      '@docusaurus/plugin-content-blog',
-      {
-        include: ['*.md', '*.mdx'],
-        path: 'blog',
-      },
-    ],
-  ],
-};
-```
-
-Docusaurus can also load plugins from your local directory, you can do something like the following:
-
-```jsx
-const path = require('path');
-
-module.exports = {
-  plugins: [path.resolve(__dirname, '/path/to/docusaurus-local-plugin')],
-};
-```
-
-## Basic Plugin Definition
-
-Plugins are modules which export a function that takes in the context, options and returns a plain JavaScript object that has some properties defined.
-
-For examples, please refer to several official plugins created.
-
-```jsx
-const DEFAULT_OPTIONS = {
-  // Some defaults.
-};
-
-// A JavaScript function that returns an object.
-// `context` is provided by Docusaurus. Example: siteConfig can be accessed from context.
-// `opts` is the user-defined options.
-module.exports = function(context, opts) {
-  // Merge defaults with user-defined options.
-  const options = {...DEFAULT_OPTIONS, ...options};
-
-  return {
-    // A compulsory field used as the namespace for directories to cache
-    // the intermediate data for each plugin.
-    // If you're writing your own local plugin, you will want it to
-    // be unique in order not to potentially conflict with imported plugins.
-    // A good way will be to add your own project name within.
-    name: 'docusaurus-my-project-cool-plugin',
-
-    async loadContent() {
-      // The loadContent hook is executed after siteConfig and env has been loaded
-      // You can return a JavaScript object that will be passed to contentLoaded hook
-    },
-
-    async contentLoaded({content, actions}) {
-      // contentLoaded hook is done after loadContent hook is done
-      // actions are set of functional API provided by Docusaurus. e.g: addRoute
-    },
-
-    async postBuild(props) {
-      // after docusaurus <build> finish
-    },
-
-    // TODO
-    async postStart(props) {
-      // docusaurus <start> finish
-    },
-
-    // TODO
-    afterDevServer(app, server) {
-      // https://webpack.js.org/configuration/dev-server/#devserverbefore
-    },
-
-    // TODO
-    beforeDevServer(app, server) {
-      // https://webpack.js.org/configuration/dev-server/#devserverafter
-    },
-
-    configureWebpack(config, isServer) {
-      // Modify internal webpack config. If returned value is an Object, it
-      // will be merged into the final config using webpack-merge;
-      // If the returned value is a function, it will receive the config as the 1st argument and an isServer flag as the 2nd argument.
-    },
-
-    getPathsToWatch() {
-      // Path to watch
-    },
-
-    getThemePath() {
-      // Returns the path to the directory where the theme components can
-      // be found.
-    },
-
-    getClientModules() {
-      // Return an array of paths to the modules that are to be imported
-      // in the client bundle. These modules are imported globally before
-      // React even renders the initial UI.
-    },
-  };
-};
-```
-
-#### References
-
-- https://v1.vuepress.vuejs.org/plugin/option-api.html