docs: adding an index for upgrade pages.

[zbwright]

Contributing guidelines

Please read our contribution workflow before submitting a pull request.

[heyitsanthony]

The describes... parts after the links seem redundant since the link already describes the target document.

[zbwright]

Agreed. We wanted it to be more than a list, but I didn't come up with anything more substantial. Maybe, for this page, it just remains a list? @joshix

[athai]

I think this may be easier to read if you bolded each subheading.

[zbwright]

Also agreed. We don't have any of these sorts of pages yet. Part of this exercise will be defining the format.

[joshix]

headings suffice. Line 5 is a h2 (##), and so on

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@46ee06a). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #8291   +/-   ##
=========================================
  Coverage          ?   76.33%           
=========================================
  Files             ?      346           
  Lines             ?    27056           
  Branches          ?        0           
=========================================
  Hits              ?    20652           
  Misses            ?     4919           
  Partials          ?     1485

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 46ee06a...385ed64. Read the comment docs.

[heyitsanthony]

This should probably be linked in docs.md or have a README.md symlink pointing to itself in the upgrades directory since right now it's unreachable from any other repo doc

[zbwright]

The files linked from this page are all listed in docs.md, down at the bottom of the page under "Upgrading and compatibility". Should I add a link to this page as well?

[heyitsanthony]

@zbwright probably include it as an 'Upgrading' link under 'Maintenance' so the doc isn't dangling and remove the old upgrading section so there's no duplication?

[heyitsanthony]

@zbwright please squash and this should be good to merge. Thanks!