Add placeholder value to canonical tag editor

[jonoalderson]

• I've read and understood the contribution guidelines.
• I've searched for any related issues and avoided creating a duplicate issue.

Current behaviour

The Canonical URL field in the advanced section of the Yoast post meta editor is blank if no value is set. E.g.,

Proposed behaviour

I propose, when no value is set, the post/page's permalink should be set as the placeholder value. E.g.,

If I wish to change the canonical URL, it'd be helpful to see the current (assumed/default) value in situ.

[jdevalk]

Agreed, that's an improvement.

[amboutwe]

Please inform the customer of conversation # 434048 when this conversation has been closed.

[amboutwe]

Please inform the customer of conversation # 428938 when this conversation has been closed.