Move plugin docs to plugin folders

Summary: Moved plugin documentation and related assets to plugin folders, fixed links and configured redirects where required. Now these docs are used for both showing docs in Flipper and generating Flipper docs website.

Reviewed By: passy

Differential Revision: D29465567

fbshipit-source-id: 3ec4240b215b0d5baea5154f64266a9ba7ead3a5

desktop/plugins/public/fresco/docs/overview.mdx

@@ -0,0 +1,27 @@
+import useBaseUrl from '@docusaurus/useBaseUrl';
+
+The images plugin allows you to inspect what images were fetched, where they are
+coming from and selectively clear caches. Currently, the plugin supports
+[Fresco](https://github.com/facebook/fresco/) as backend.
+
+<img alt="Images plugin" src={useBaseUrl("img/images-plugin.png")} />
+
+## Cache Inspector
+
+Images are grouped by the different caching layers they are stored in. The current
+fill rate of the cache is shown and you can choose to selectively clear caches.
+
+
+## Attribution
+
+Images can be annotated with attributes that can help to determine the context in
+which an image was loaded and displayed. You can use that information to filter
+by a particular surface or only inspect images that are in the critical path
+of your application, for instance during cold start.
+
+## Leak Tracking
+
+Dealing with large resources can require special APIs to be used that circumvent
+usual garbage collection. The plugin allows tracking `CloseableReference`s for
+Fresco on Android that weren't properly closed, which can help you improve
+the performance of your app.