Moz-fluent-linter

* Add `--version` command
* Improve parsing (HTML tags with multiple attributes)
* Flag files without empty line at the end
* Add feature gate for variable references

**Full Changelog**: https://github.com/mozilla-l10n/moz-fluent-linter/compare/v0.2.2...v0.2.3

Add check for missing empty line at the end of Fluent files.

Added missing Python dependencies needed by fluent-syntax