feat: add normalize xml hook

[vaahtokarkki]

Normalize XML

Add normalize XML pre-commit hook. By default, it applies to .xml, .ui, and .qml files. Note that .qml files are allowed to contain invalid XML.

Usage:

- repo: https://github.com/nlsfi/qgis-plugin-dev-tools
  rev: tag
  hooks:
    - id: normalize-xml
      args: [
        "--remove-tag", "fieldConfiguration",
        "--remove-tag", "editable",
        "--remove-tag", "labelOnTop",
        "--remove-tag", "reuseLastValue",
        "--remove-tag", "editforminitcode",
      ]

[Joonalai]

Great work! Good idea to not require installing other than lxml to run this hook. Just add section to README.md and you are good to go 😄