docs: move summary to README (#7816)

* Move documentation summary to docs README

* Delete SUMMARY.md

Co-authored-by: Tim Lai <timothy.lai@gmail.com>

Author: ravage84

docs/README.md

@@ -2,4 +2,23 @@
 
 Welcome to the Swagger UI documentation!
 
-A table of contents can be found at `SUMMARY.md`.
+## Usage
+
+- [Installation](usage/installation.md)
+- [Configuration](usage/configuration.md)
+- [CORS](usage/cors.md)
+- [OAuth2](usage/oauth2.md)
+- [Deep Linking](usage/deep-linking.md)
+- [Limitations](usage/limitations.md)
+- [Version detection](usage/version-detection.md)
+
+## Customization
+
+- [Overview](customization/overview.md)
+- [Plugin API](customization/plugin-api.md)
+- [Custom layout](customization/custom-layout.md)
+
+## Development
+
+- [Setting up](development/setting-up.md)
+- [Scripts](development/scripts.md)