Creates `Third Party` documentation section

I think it would be great to create a section in our documentation to listing some contents built with `returns`, I have some examples from [__agones__](https://agones.dev/site/):

* [Videos and Presentations](https://agones.dev/site/docs/third-party-content/videos-and-presentations/)
* [Podcasts](https://agones.dev/site/docs/third-party-content/podcasts/)
* [Libraries and Tools](https://agones.dev/site/docs/third-party-content/libraries-tools/)