add discussions to contribution graph

[bdresser]

Why:

Documentation is out of date! Discussion activity shows up on the contribution graph.

What's being changed:

adds "opened a discussion; answered a discussion" to list of activities that show in contribution graph.

Check off the following:

• I have reviewed my changes in staging. (look for the deploy-to-heroku link in your pull request, then click View deployment)
• For content changes, I have reviewed the localization checklist
• For content changes, I have reviewed the Content style guide for GitHub Docs.

[welcome]

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[evi-liu]

thank you for opening this PR! 🙌

[janiceilene]

Thanks so much for opening a PR @bdresser! This change looks 💯 I'll update the branch and get this merged 🚀

Edit: I just saw @cheshire137 is requested for review, so I'll hold off until that's done 👍

[cheshire137]

This is accurate!

[janiceilene]

Thanks folks! I'll update the branch and get this merged in soon ⚡

[github-actions]

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