Promote contribution to projects

[benaadams]

The website doesn't promote getting members and others to contribute to .NET Foundation projects.

As a contributor it seems a natural consequence of OSS to me; but that's only implied; as obviously contributors are just a tiny fraction of OSS users so it may not occur to most people or they may not know where or how to get started.

We should provide (or link to) a guide on how to get started; and surface projects looking for help and sponsorship (similar to @daveaglick's https://discoverdot.net/projects/) for .NET Foundation projects in a prominent fashion. (Then obs promote people to look at the page periodically via social media, newsletters etc 😉)

[pascalberger]

@benaadams Is this solved with project spotlights: https://dotnetfoundation.org/projects/spotlight?