Sync this repo against upstream, squash prototype branches, merge

[atc0005]

I need to start the work to prepare this repo to be a complete fork.

I've tried multiple times to reach the original developer in recent months (GitHub repo, Twitter, direct email), all to no avail. It appears that if I wish to develop this code further I'll need to maintain my own fork separate from upstream.

Hopefully I'll hear back at some point and this repo can go back to being a PR-fork only, but until then I can move forward with queued changes.

[atc0005]

Going to work on including this as a follow-up release and instead focus on the working the other unreleased changes as a minor patch release (no change in package behavior).

[atc0005]

This release can target these upstream GitHub issues:

• Remote API error handling: expose response string dasrick/go-teams-notify#15
• Proposal: Add formatting functions useful for text conversion dasrick/go-teams-notify#16
• Fix whitespace linting error dasrick/go-teams-notify#21
  • might already be resolved?

Once this is done, I'll close out the existing upstream Pull Requests with a note that the behavior is included in this fork.

[atc0005]

Most of this work is complete.

Next: some light work to the README to explain/note that this fork is now standalone.