Add alt-require as a default rule

[Polarpi]

Describe the bug
The rule alt-require is currently not a default rule. However, it should be added to encourage using the alt attribute on all imgs.

To Reproduce
Steps to reproduce the behavior:

1. open new html file with default rules
2. does not flag a warning

Expected behavior
We want all imgs to have an alt tag (can be empty)
Also requires text areas with href attribute to have alt tag
Input tags with type="image" should have alt tag

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.