ci: check pull request titles (#3)

Copies `pr-title.yml` from lazysecrets: a pull request title must start with a conventional commit type (`feat: …`, `fix(scope): …`, `[feat] …`).

Pull requests are squash-merged, so the title becomes the commit on main. Keeping those conventional means release notes can be written from main's history later (git-cliff, as lazysecrets does).

Once merged, `PR title / *` gets added to main's required checks.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Reviewed-on: #3
Co-authored-by: Karl-Einar Bergstrøm <karl-einarb@outlook.com>

renovate.json

@@ -0,0 +1,6 @@
+{
+  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
+  "extends": [
+    "local>keb/renovate"
+  ]
+}