docs: add aur checklist

packaging/aur/RELEASE.md

@@ -0,0 +1,23 @@
+# AUR Release Checklist
+
+1. Update PKGBUILD: pkgver, sha256sums
+2. Test locally
+3. Update .SRCINFO
+4. Commit & push to AUR
+
+**Test**
+```bash
+makepkg -si
+```
+
+**Generate .SRCINFO**
+```bash
+makepkg --printsrcinfo > .SRCINFO
+```
+
+**Push to AUR**
+```bash
+git add PKGBUILD wgtunnel-bin.install .SRCINFO
+git commit -m <message>
+git push origin master
+```