Add worker-src

The patch from #2 works well with 7.x-1.11.

Also confirmed that worker-src configuration is exportable via Features.

The patch failed to apply.

After this patch was created, there have been commits done to fix three issues.

• ✨ Text fields not big enough Fixed
• ✨ Add support for feature-policy header Fixed
• 📌 Skip report-uri processing if value is empty Fixed

Those issues changed the same files this patch is changing too. That is why the provided patch does not apply anymore.

Rerolled the patch as per #6

@bharath-kondeti in the latest 7.x-1.x fields don't need to be listed explicitly in _seckit_csp(). Also, they do need to be listed in seckit_admin_form_validate().

Here's a reroll.