docs(*) add 1.9.0 changes

[rainest]

Add 1.8.3 changes and release instructions.

Small, but we haven't had a patch release in quite a while, and the error return is something we want in KIC sooner or later.

I also want to confirm the new CI stuff works in the actual deck repo and confirm if there's something I forgot that still requires manual work.

Added release instructions since we'd apparently forgotten to ever take them out of a Google Doc, and they've been stable for a while now.

[codecov-commenter]

Codecov Report

Merging #535 (6b1258b) into main (65b1bee) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #535   +/-   ##
=======================================
  Coverage   51.98%   51.98%           
=======================================
  Files          73       73           
  Lines        7714     7714           
=======================================
  Hits         4010     4010           
  Misses       3354     3354           
  Partials      350      350           

---

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 65b1bee...6b1258b. Read the comment docs.

[mflendrich]

If I understand correctly, each of these changes modifies existing behavior that may potentially be relied upon (per Hyrum's law).

Therefore I suggest that we bump the minor version number and release this as 1.9.0, and replace "Fixed" with "Breaking changes" in the changelog.

[mflendrich]

Since the last round, I'm now convinced that the select-tags change can be deemed a fix; I don't feel very comfortable doing so for the semantic change of error handling, but (as discussed in the inline comment) the impact is minimal (this is becoming an academic discussion) and not worth agonizing over it, so let it be.

Some minor release procedure comments attached.