feat: cleanup docker setup

- Add .dockerignore
- Replace .env with .env.example
- Add migrations service
- Cleanup Dockerfile: simpler setup, simpler copy, no migrations inside the image
- Update README to match new instruction

.dockerignore

@@ -0,0 +1,20 @@
+node_modules/
+.env
+.git/
+.gitignore
+.npmrc
+.dockerignore
+.DS_Store
+npm-debug.log
+logs/
+tmp/
+coverage/
+dist/
+*.md
+*.tar.gz
+*.zip
+Dockerfile
+
+nsecbunker.json
+connection.txt
+config