prop-name-casing autofix removes $ in prop name

[privatenumber]

Tell us about your environment

• ESLint version: 5.15.3
• eslint-plugin-vue version: 5.2.2
• Node version: 8.12.0

What did you do?
eslint --fix

What did you expect to happen?
For renaming to happen on non-camelCase props.

What actually happened?
My prop name $actionEl (which I know has another problem of it's own) was renamed to actionEl.

[mysticatea]

Thank you for the report.

I could reproduce it on our online demo.

[privatenumber]

In addition to fixing the autofix logic here, it might be worth introducing a rule to prevent non-alphanumerical characters in prop names.