Issue #366 - Make URL validation on input event instead of change event

[BhargavBhandari90]

Description of the Change

Changed event for "Redirect From" field for URL validation.

• Previously it was on a change event, so validation was not happening unless we click out of the text field. Because of that publish button disabling was irregular and confusing.
• So made it on keyup event and added ajax abort to avoid simultaneous requests.
• Also added a typing wait time of 850 ms so when user stops typing, then URL validation will happen.
• Based on this validation process, disabling/enabling submit button became regular now.
• Also added a loding icon when user start typing, so that they know something is happening.

Video for better understanding for above bullet points https://somup.com/cZnTI6pzGz

Closes #366

How to test the Change

• Go to WP admin --> Tools --> Safe Redirect Manager
• Click "Create Redirect Rule"
• Start typing into "Redirect From" and stop typing
• Remove some characters and stop
• Observe the submit button active/inactive state

Changelog Entry

Changed - URL validation check on "input" event for "Redirect From" field

Credits

@BhargavBhandari90, @peterwilsoncc

Checklist:

• [x] I agree to follow this project's Code of Conduct.
• [x] I have updated the documentation accordingly.
• [ ] I have added tests to cover my change.
• [ ] All new and existing tests pass.

[BhargavBhandari90]

Thank you @peterwilsoncc for your suggestions.

[jeffpaul]

@peterwilsoncc back to you for review/approval/merging