Add help message on entity form field

Assigning to myself as I'm triaging all RTBC issues.

The patch still applies and it does what is expected. See screenshots. To be honest, I'm not loving the wording, so I will see if I can come up with something right now.

@aobah When reviewing, please do not add the patch that was already included. Thanks.

@lucienchalom When moving to RTBC, please explain whether you reviewed the code or tested the patch or both. For testing, explain the testing process. Thanks.

Forgot my screenshots:

Before:

After:

I reworded it to be more helpful (IMO). I'd like someone to review the wording before I commit this patch.

Before:

This field is for others URLs to be redirected to.

After:

Click the "Add URL redirect" button and enter a URL that will redirect to this content. If the URL of this content ever changes, adding a URL redirect ensures your users will find this content when using the old URL.

Thanks for following up on this, Kristen. Instead of "your users" how about "visitors"?

Thanks, Damien. I’ll try to make this change later today.j

I have updated the changes suggested in #16. Please review.

Nice… thanks @sourabhjain and thanks for the interdiff even though the patch is tiny :) I might be able to test and merge tonight or tomorrow.

Hi everyone I´ve been reviewing the patch proposed by sourabhjain in #18 and I notice that the text it´s right. Attached evidence.