Add build script to slim down docker images

build.sh

@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+
+if command -v yarn >/dev/null 2>&1; then
+    echo "yarn is available"
+else
+    echo "yarn is not installed" >&2
+    exit 1
+fi
+
+yarn install
+
+yarn build