Added build script for v2

Author: zegl

hack/build-v2.sh

@@ -0,0 +1,16 @@
+#!/bin/bash
+
+set -euo pipefail
+
+git stash
+git checkout v2
+git merge main --no-edit
+
+# Build
+yarn build
+yarn package
+git add lib dist || true
+git commit -m "Build action" --allow-empty
+
+# Push
+git push -u origin v2:v2