dart format and update the readme

[devoncarew]

• run dart format on the repo (to see if this fixes the CI)
• add a badge to the readme file

[lrhn]

Seems innocuous, even if I preferred the previous formatting for the uflags.dart file.

[devoncarew]

Thanks for merging! I think you'll need to re-enable github actions:

[lrhn]

Let me try.
I have no idea what Github actions are, so maybe I should just disable it entirely. Doesn't seem important for such a simple package.

[devoncarew]

Ah, github actions is just the name for the continuous integration system available from github. The configuration file for it in this repo - https://github.com/lrhn/charcode/blob/master/.github/workflows/ci.yml - is a little harder to read then it needs to be for what it does.

For every PR, and every merge into master, it runs pub get, verifies that the source is formatted, analyzes the code, and runs the tests. It's definitely a value add :)