Documentation: link to GitHub Discussions

[Jinksi]

👋 Hi PyTorch Lightning community!

As a newcomer to PyTorch Lightning, I feel that the community on here (Discussions) is really the place to be to connect with each other and get help if needed.

In the docs, there is a link to Developer Resources that is ⚠️currently broken, it was linking to Community Examples.

💡 I propose that this link could instead point to GitHub Discussions to help people "Find resources and get questions answers"

I'd be glad to submit a PR with this change if suitable.

[awaelchli]

Yes please! I like this idea!