ci(fork): run Validate lime-elements on PRs targeting lime

[adrianschmidt]

What

Add lime to the base-branch filter of the Validate lime-elements workflow trigger:

 on:
   pull_request:
-    branches: [main]
+    branches: [lime, main]

Why

The workflow came over from upstream jgroth/kompendium and only triggered on PRs to main. But this fork's default branch is lime, and all fork PRs target lime — so the check never ran (PR #6 shows only Block Autosquash / CI / Lint; the workflow has zero runs).

For pull_request, the branches filter matches the PR's base branch, so adding lime is what makes it fire on our PRs. main is kept for any main-targeted PRs and to minimize divergence from upstream.

Nothing else needed adapting: the workflow already checks out the public Lundalogik/lime-elements@main, and the build/link steps are repo-agnostic.

Self-test

This PR's base is lime and its head contains the new trigger, so the Validate lime-elements check should run on this PR itself.

Note

This is a fork customization on a file that sync-upstream.yml pulls from upstream, so future syncs may conflict on this line — expected and trivial to resolve.