Implement main class & fetch function - including robust error handling.

tsconfig.json

@@ -107,6 +107,6 @@
     // "skipDefaultLibCheck": true,                      /* Skip type checking .d.ts files that are included with TypeScript. */
     "skipLibCheck": true                                 /* Skip type checking all .d.ts files. */
   },
-  "include": ["src/**/*"],
+  "include": ["src/**/*.ts"],
   "exclude": ["node_modules"],
 }