Add gccrs joint collaboration blogpost

[CohenArthur]

Hi folks,

This PR adds the content of the "joint gccrs blogpost" which I've written over the past few weeks, with the help of multiple reviewers from the project. You can find the discussion here, and a link to the draft containing the review comments here.

Very happy to answer any questions you may have or to fix any formatting/wording/content issues. Let me know if there's anything I can do to make the reviewing process easier.

Please also note that the blogpost was untitled until now, and I'm not sure this is a good name or fits any titling conventions. Please shout if you have any suggestions!

Thanks all :heart:

Rendered

[ehuss]

@eholk Can you take point on this?

[joshtriplett]

Huge thanks to @CohenArthur for working on this post and for taking so much care to maintain a collaborative and cooperative relationship with the Rust project.

[cuviper]

Don't forget to update the date in the path!

[eholk]

Don't forget to update the date in the path!

I will before merging. I'll plan on doing that tomorrow since I put a call in Zulip for any final comments from the council and I want to make sure they all get a chance to see it before I merge this.

[CohenArthur]

Rebased on latest master and force-pushed. The new changes reflect @oli-obk's and @comex's suggestions on Zulip and HackMD