Draft: feat(announcements): Add support for customizable homepage

[GabDug]

Hey, I just made a Pull Request!

This MR integrates with the custom homepage of the @backstage/plugin-home plugin.

This plugin will manage the card and the layout, hence the need to extract the "inner" content of the AnnouncementsCard in another component, so the card logic can be managed by the custom home plugin.

For custom homepage users:

• Added a ready to use HomepageAnnouncements to drop into the <CustomHomepageGrid>
• Exported the inner content of the card, so users can declare their own cards as code for further customization
• TODO: Added tests and documentations with screenshots for the two integrations methods

For plugin maintainers:

• Updated the dev app to include the custom home, with a default configuration

Screenshot of the dev app"

:heavy_check_mark: Checklist

• [x] A changeset describing the change and affected packages. (more info)
• [ ] Added or updated documentation
• [ ] Tests for new functionality and regression tests for bug fixes
• [X] Screenshots attached (for UI changes)
• [X] All your commits have a Signed-off-by line in the message. (more info)

[backstage-goalie[bot]]

Changed Packages

Package Name	Package Path	Changeset Bump	Current Version
app	workspaces/announcements/packages/app	none	v0.0.0
@backstage-community/plugin-announcements	workspaces/announcements/plugins/announcements	minor	v0.5.9

[github-actions[bot]]

This PR has been automatically marked as stale because it has not had recent activity from the author. It will be closed if no further activity occurs. If the PR was closed and you want it re-opened, let us know and we'll re-open the PR so that you can continue the contribution!