Link new-ish md files and WWDC sessions (#5880)

This should improve the discoverability of these resources.

Author: neonichu

Documentation/Plugins.md

@@ -376,3 +376,8 @@ The `XcodePluginContext` input structure is similar to the regular `PluginContex
 If any targets are chosen in the Xcode user interface, Xcode passes their names as `--target` arguments to the plugin.
 
 It is expected that other IDEs or custom environments that use SwiftPM could similarly provide modules that define new entry points and extend the functionality of the core `PackagePlugin` APIs.
+
+### References
+
+- "Meet Swift Package plugins" [WWDC22 session](https://developer.apple.com/videos/play/wwdc2022-110359)
+- "Create Swift Package plugins" [WWDC22 session](https://developer.apple.com/videos/play/wwdc2022-110401)

Documentation/README.md

@@ -17,9 +17,11 @@ We’ve designed the system to make it really easy to share packages on services
     * [Dependency Hell](#dependency-hell)
 * [Using packages](Usage.md)
 * [Package manifest specification](PackageDescription.md)
+* [Getting Started with Plugins](Plugins.md)
 * [Package discovery with Package Collections](PackageCollections.md)
 * [Package Registry service specification](Registry.md)
 * [Using SwiftPM as a library](libSwiftPM.md)
+* [Using Module Aliasing](ModuleAliasing.md)
 
 ***
 

README.md

@@ -31,7 +31,7 @@ Please use [this guide](https://swift.org/getting-started/#using-the-package-man
 
 For Quick Help use the `swift package --help` command.
 
-For documentation on using Swift Package Manager, creating packages, and more, see the [documentation directory](Documentation).
+For documentation on using Swift Package Manager, creating packages, and more, see the [documentation directory](Documentation/README.md).
 
 For documentation on developing the Swift Package Manager itself, see the [contribution guide](CONTRIBUTING.md).