feat: Add head component

[istarkov]

Description

Allows Head component

Hidden under headSlotComponent flag

Vercel fixture now have a HTMLRewriter example. Improves development.

Todo In Next PR

• Head Title support

• Icons

• Allow reset as field

• - BG is now white always

• - It's shown as fixed element to not break layout

Implementation details

This component has more priority above PageSettings meta tags
e.g. If some tag exists in PageSettings and in HeadSlot the HeadSlot wins

Steps for reproduction

Create HeadSlot

• - Visit https://webstudio-fixture-project-a-0su3o.wstd.work/head-tag
  check server response.

See og:title is not duplicated.

• - Check Elements Panel

See no duplicated. All tags exists.

• - Click Home.
  See no meta tags are in Elements panel from /head-tag page

• - Click back button

See all meta is rendered and is not duplicated.

Code Review

• hi @kof, I need you to do
  • conceptual review (architecture, feature-correctness)
  • detailed review (read every line)
  • test it on preview

Before requesting a review

• made a self-review
• added inline comments where things may be not obvious (the "why", not "what")

Before merging

• tested locally and on preview environment (preview dev login: 0000)
• updated test cases document
• added tests
• if any new env variables are added, added them to .env file

[johnsicili]

Good stuff!! 🔥

IMO we should set a background to this and the XML page because when the theme is dark it's hard to read.

Also set to full width

[istarkov]

Good stuff!! 🔥

IMO we should set a background to this and the XML page because when the theme is dark it's hard to read.

Also set to full width

div is already a full width.

For background I can set something like white with 50% opacity would be visible in most cases

[istarkov]

Probably we need to show it as absolute element above content. So it will not break the existing layout

[istarkov]

Background fixed now white