Add compatibility documentation for indirectly supported packages

[MrAlias]

The following packages are supported by the auto-instrumentation; they will produce telemetry through the net/http instrumentation that under-pins them.

• Gorilla Mux
• Gin

Each of these packages need to be added to the compatibility documentation as supported packages. However, the exact versions that are supported is not immediately obvious.

In the process of resolving this a strategy (preferably automated) to determine version support needs to be developed.

Originally posted by @grcevski in #907 (comment)