Add linter for common issues
There are some fairly simple, common issues that we might be able to detect and warn about automatically.
- Accessibility: Button/entry/etc. with no label, tooltip, or accessibility labelled-by.
- HIG: Have a list of "user-facing" text properties (Label:label, Entry:placeholder, etc.) and check them against the HIG's typography guidelines.
Linter rules can be wrong sometimes, so if we do this, we should probably have a way to tell the linter to ignore a statement. Should it be a special comment? Some new syntax? Also might want a command line option to disable linters entirely.