feat: add non-selectable menu label

[sjelfull]

This adds a non-selectable menu label component that allow us to add headers and group certain items.

Example:

<MenuButton
  button={<Button text="Open" />}
  id="label-example"
  menu={
    <Menu>
      <Stack space={1}>
        <MenuLabel text="Label 1" />
        <MenuItem text="Item 1" />
        <MenuItem text="Item 2" />
      </Stack>
      <MenuDivider />
      <MenuLabel text="Label 2" />
      <MenuItem text="Item 3" />
    </Menu>
  }
/>

I have tried to make the label feel well integrated with the other elements, but doesn't have the full overview of what considerations I should make, so leave final decision to you @mariuslundgard

CleanShot 2025-04-10 at 11.05.08.mp4 (uploaded via Graphite)

[vercel]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

Name	Status	Preview	Comments	Updated (UTC)
sanity-ui-storybook	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Apr 10, 2025 9:21am
sanity-ui-workshop	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Apr 10, 2025 9:21am

[sjelfull]

• feat: add non-selectable menu label #1698 👈 (View in Graphite)
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.