ci: Only build Firefox for non-draft PRs (#2085)

Save some trees

.github/workflows/firefox.yml

@@ -3,6 +3,7 @@ on:
   workflow_dispatch:
   pull_request:
     branches: ["main"]
+    types: [opened, synchronize, reopened, ready_for_review]
     paths-ignore: ["*.md", "*.png", "*.svg", "LICENSE-*"]
 
 concurrency:
@@ -18,6 +19,7 @@ env:
 jobs:
   firefox:
     name: Build Firefox
+    if: github.event.pull_request.draft == false
     strategy:
       fail-fast: false
       matrix: