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

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+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.

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

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+Currently, the images plugin only supports [Fresco](https://frescolib.org/) for Android as backend, but just like the network plugin, support for other image loading libraries
+could easily be added. Send us a PR!
+
+## Fresco and Android
+
+The Fresco images plugin is shipped as a separate Maven artifact:
+
+```groovy
+dependencies {
+  debugImplementation 'com.facebook.flipper:flipper-fresco-plugin:0.30.1'
+}
+```
+
+After including the plugin in your dependencies, you can add it to the
+client:
+
+```java
+import com.facebook.flipper.plugins.fresco.FrescoFlipperPlugin;
+
+client.addPlugin(new FrescoFlipperPlugin());
+```
+
+The `FrescoFlipperPlugin` constructor offers a whole lot of configuration options which
+can be useful if you have an advanced setup of Fresco in your application:
+
+
+```java
+FrescoFlipperPlugin(
+      DebugImageTracker imageTracker,
+      PlatformBitmapFactory bitmapFactory,
+      @Nullable FlipperObjectHelper flipperObjectHelper,
+      DebugMemoryManager memoryManager,
+      FlipperPerfLogger perfLogger,
+      @Nullable FrescoFlipperDebugPrefHelper debugPrefHelper,
+      @Nullable CloseableReferenceLeakTracker closeableReferenceLeakTracker) { ... }
+```
+
+### Leak Tracking
+
+The Flipper plugin can help you track down `CloseableReferences` who have not had
+`close()` called on them. This can have a negative impact on the performance of
+your application.
+
+To enable this functionality, you need to create a `CloseableReferenceLeakTracker`
+and set it in both your `ImagePipelineConfig` for Fresco and the `FrescoPluginPlugin`
+on creation.
+
+```java
+import com.facebook.imagepipeline.debug.FlipperCloseableReferenceLeakTracker;
+
+// ...
+
+FlipperCloseableReferenceLeakTracker leakTracker = new FlipperCloseableReferenceLeakTracker();
+
+new ImagePipelineConfig.Builder()
+    // ...
+    .setCloseableReferenceLeakTracker(leakTracker)
+    .build();
+
+
+client.addPlugin(new FrescoFlipperPlugin(
+    new FlipperImageTracker(),
+    Fresco.getImagePipelineFactory().getPlatformBitmapFactory(),
+    null,
+    new NoOpDebugMemoryManager(),
+    new NoOpFlipperPerfLogger(),
+    null,
+    leakTracker));
+```
+
+### Attribution
+
+In order to annotate images with the context they are used in, you have to set a
+caller context when loading the image. This can be any object, so for the simplest
+case, a String will suffice.
+
+```java
+String callerContext = "my_feature";
+
+// For DraweeViews:
+draweeView.setImageURI(uri, callerContext);
+
+// For prefetching:
+ImagePipeline imagePipeline = Fresco.getImagePipeline();
+imagePipeline.prefetchToDiskCache(imageRequest, callerContext);
+
+// For manually fetching an image:
+DataSource<CloseableReference<CloseableImage>>
+    dataSource = imagePipeline.fetchDecodedImage(imageRequest, callerContext);
+```
+
+If a caller context is supplied, the image will be properly attributed in the
+Flipper image plugin.