New component: Standalone popover element

[splashdust]

<gds-popover> was previously only used as an internal primitive in other components, such as the Datepicker and Dropdown. This PR promotes it to a public standalone component that can be used for various popover needs.

API has been simplified and made more declarative, allowing you to specify the trigger/anchor element in a slot:

<gds-popover>
  <gds-button slot="trigger">Click to open popover</gds-button>
  <p>This is the content that will display in the popover!</p>
</gds-popover>

[green-design-system-bot[bot]]

🦋 Changeset status

Based on the included changeset, the following releases will be published as a result of this PR:

• @sebgroup/green-angular: 4.0.0 → 4.1.0 (minor bump)
• @sebgroup/green-core: 1.21.2 → 1.22.0 (minor bump)

Note: If unpublished changesets where merged to main after the first commit of this PR, this list will include those changes in addition to the ones specific to this PR.

[green-design-system-bot[bot]]

👋 Thanks for creating a pull request!

🚀 Checkout the storybooks we've created for it:

• angular
• angular-charts
• chlorophyll
• core
• react
• react-charts