Upgrades check-spelling to v0.0.21
The command to apply changes should now work on Windows (it requires
Perl, but I believe that's more or less present most of the time, and it
should walk you through the rest of the required tools).
There are a bunch of new features, the most important here are probably
being able to update the metadata from Windows. (If it doesn't work,
please @ me).
Also, candidate.patterns will automatically suggest patterns. You can
see them in patterns.txt, e.g.:
```
# Automatically suggested patterns
# hit-count: 3831 file-count: 582
# IServiceProvider
\bI(?=(?:[A-Z][a-z]{2,})+\b)
```
The metadata bits (the hit count/file count) don't have to be retained
(I hope they'll be useful in deciding whether/or not to add a pattern,
i.e. "how applicable is it?"), the comment hinting at what the pattern
does is probably worth retaining.
We've been using more or less this version for a while internally
(including talk-to-bot, and, I do have a pattern that could be used to
let people use that in forks, but, I'm going to skip that for now).
This weekend, I did some cleanup for `act` (to run check-spelling
locally), and some minor polish.
You can see the runs I made in
https://github.com/check-spelling/terminal/actions
