Multiple deploy keys

[tarrenj]

Adds instructions on defining unique ssh keys (deploy keys) per repo on one server by using the ssh config file.

Why:

#500

What's being changed:

Check off the following:

• All of the tests are passing.
• I have reviewed my changes in staging.
• For content changes, I have reviewed the localization checklist
• For content changes, I have reviewed the Content style guide for GitHub Docs.

[welcome]

Thanks for opening this pull request! A GitHub docs team member should be by to give feedback soon. In the meantime, please check out the contributing guidelines.

[janiceilene]

Thanks for opening a PR @tarrenj! I'll get this triaged for review ✨

[tarrenj]

Found and fixed a small typo, sorry if this bounces it back into Triage!

[martin389]

@tarrenj - thanks so much for creating this PR! 🎉

I've added some small edits to the draft, just to suit our existing docs conventions. Could you check that you're happy with my suggestions? 👍

You can find the rendered preview here: https://docs-501--multiple-deploy-keys.herokuapp.com/en/free-pro-team@latest/developers/overview/managing-deploy-keys#using-multiple-repositories-on-one-server

[tarrenj]

@martin389

I've added some small edits to the draft, just to suit our existing docs conventions. Could you check that you're happy with my suggestions? 👍

They look good to me! I used this existing page as a reference, so that's another discrepancy for you guys to be aware of.

[martin389]

Checked with the folks from support, and they're happy with this draft 🎉

[martin389]

Now doing some readiness checks.

[lucascosti]

Some versioning for the different page versions is probably needed, plus a few suggestions to clarify the behavior.