docs: fix and improve React examples

[rajington]

What is it?

• Docs / tests

Description

Some React examples had unnecessary $ or missed things like key (which would be good to call out if qwik behaves differently).

Use cases and why

• 1. Better comparison to status quo

Checklist:

• My code follows the developer guidelines of this project
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• [NA] Added new tests to cover the fix / functionality

[farukEncoded]

Actually, you will need those $ signs here. and also an extra pair of curly braces. like this

style={{
      'background': `rgb(${red}, ${green}, ${blue})`
    }}

[manucorporat]

Thanks a lot for the PR! merged!