[docs] Add missing App Arch READMEs. (#82080)

docs/developer/plugin-list.asciidoc

@@ -323,8 +323,8 @@ Failure to have auth enabled in Kibana will make for a broken UI. UI-based error
 |The deprecated dashboard only mode.
 
 
-|{kib-repo}blob/{branch}/x-pack/plugins/data_enhanced[dataEnhanced]
-|WARNING: Missing README.
+|{kib-repo}blob/{branch}/x-pack/plugins/data_enhanced/README.md[dataEnhanced]
+|The data_enhanced plugin is the x-pack counterpart to the OSS data plugin.
 
 
 |{kib-repo}blob/{branch}/x-pack/plugins/discover_enhanced/README.md[discoverEnhanced]

examples/bfetch_explorer/README.md

@@ -0,0 +1,11 @@
+## bfetch explorer
+
+bfetch is a service that allows you to batch HTTP requests and stream responses
+back.
+
+This example app demonstrates:
+ - How you can create a streaming response route and consume it from the
+   client
+ - How you can create a batch processing route and consume it from the client
+
+To run this example, use the command `yarn start --run-examples`.

examples/embeddable_examples/README.md

@@ -0,0 +1,4 @@
+## Embeddable examples
+
+This example plugin exists to support the `embeddable_explorer` app.
+

examples/embeddable_explorer/README.md

@@ -0,0 +1,10 @@
+## Embeddable explorer
+
+This example app shows how to:
+ - Create a basic "hello world" embeddable
+ - Create embeddables that accept inputs and use an EmbeddableRenderer
+ - Nest embeddables inside a container
+ - Dynamically add children to embeddable containers
+ - Work with the EmbeddablePanel component
+
+To run this example, use the command `yarn start --run-examples`.

examples/state_containers_examples/README.md

@@ -0,0 +1,8 @@
+## State containers examples
+
+This example app shows how to:
+ - Use state containers to manage your application state
+ - Integrate with browser history and hash history routing
+ - Sync your state container with the URL
+
+To run this example, use the command `yarn start --run-examples`.

x-pack/plugins/data_enhanced/README.md

@@ -0,0 +1,25 @@
+# data_enhanced
+
+The `data_enhanced` plugin is the x-pack counterpart to the OSS `data` plugin.
+
+It exists to provide Elastic-licensed services, or parts of services, which
+enhance existing OSS functionality from `data`.
+
+Currently the `data_enhanced` plugin doesn't return any APIs which you can
+consume directly, however it is possible that you are indirectly relying on the
+enhanced functionality that it provides via the OSS `data` plugin.
+
+Here is the functionality it adds:
+
+## KQL Autocomplete
+
+The OSS autocomplete service provides suggestions for field names and values
+based on suggestion providers which are registered to the service. This plugin
+registers the autocomplete provider for KQL to the OSS service.
+
+## Async, Rollup, and EQL Search Strategies
+
+This plugin enhances the OSS search service with an ES search strategy that
+uses async search (or rollups) behind the scenes. It also registers an EQL
+search strategy.
+