🌞 [Other]: Implement PR Supersedence for Font Data Updater

[MariusStorhaug]

Description

The font data updater should automatically close older update pull requests when it opens a new PR, mirroring dependabot's supersedence behavior. When a new update PR is created, any previous open update PRs should be detected and closed. Additionally, when an update PR is merged and the font data file is updated, any previous related PRs (that become outdated due to the merge) should also be closed.

Requested functionality:

• Detect existing open font data update PRs when a new update PR is opened.
• Automatically close superseded PRs with a comment indicating they were replaced by a newer update.
• When an update PR is merged and the font data file is updated, ensure all previous open PRs for font data updates are closed if they are obsolete.
• Follow the behavior similar to dependabot's PR lifecycle management.

Why:
This will keep the repository tidy, prevent confusion from redundant update PRs, and streamline the review/merge process.

Optional:

• Add a configurable message to be posted when closing superseded PRs.
• Ensure changes are documented in the updater bot's README or docs.