feat: add site-wide custom scripts

[neatbyte-vnobis]

Changes

Implement issue "Ability to insert custom scripts"

How Has This Been Tested?

Manual

Documentation

None?

[SvenAlHamad]

@neatbyte-vnobis Can you please double check this one. When I insert a meta tag into the tags field, it shows up, but if I insert a simple script, like this one, it's not inserted into the page:

<script>
    alert('Hello from header');
</script>

[neatbyte-vnobis]

Closed as new pull was created (targeting new umbrella branch) - #2795