Separate Docker build into dedicated script

- Create build-image.sh for dedicated Docker image building
- Remove Docker build logic from build.sh to focus on Node.js app only
- Add comprehensive instructions for running and pushing Docker images
- Improve build script modularity and separation of concerns

package.json

@@ -1,6 +1,6 @@
 {
   "name": "jmespath-playground",
-  "version": "1.1.4",
+  "version": "1.1.5",
   "description": "A React-based web application for testing JMESPath expressions against JSON data",
   "main": "index.js",
   "scripts": {