Add Docker build + GitHub Actions CI/CD (test -> build -> publish to GHCR)

package.json

@@ -6,7 +6,9 @@
   "type": "module",
   "scripts": {
     "start": "node index.js",
-    "dev": "node --watch index.js"
+    "dev": "node --watch index.js",
+    "test": "node tests/smoke.mjs",
+    "docker": "docker build -t tg_bot_gen ."
   },
   "keywords": [
     "telegram",