Button's processing state's width and height is set to initial width and height

[ilayda21]

Done

• Added script that sets width and height of the button in processing state

Fixes #3713

QA

• Open demo
• Click on the button
• Verify button's width and height does not change

Check if PR is ready for release

If this PR contains Vanilla SCSS code changes, it should contain the following changes to make sure it's ready for the release:

• PR should have one of the following labels to automatically categorise it in release notes:
  • Feature 🎁, Breaking Change 💣, Bug 🐛, Documentation 📝, Maintenance 🔨.
• Vanilla version in package.json should be updated relative to the most recent release, following semver convention:
  • if CSS class names are not changed it can be bugfix relesase (x.x.X)
  • if CSS class names are changed/added/removed it should be minor version (x.X.0)
  • see the wiki for more details
• Any changes to component class names (new patterns, variants, removed or added features) should be listed on the what's new page.
• Documentation side navigation should be updated with the relevant labels.

[webteam-app]

Demo starting at https://vanilla-framework-4289.demos.haus

[bethcollins92]

LGTM 👍🏼

[bethcollins92]

Accessibility wise I was going to suggest adding text/aria-label to the spinner, but if we're adding disabled then screen readers will ignore the whole button anyway 😅