fix: improves error message when handler is not found (#469)

src/helper.ts

@@ -91,7 +91,7 @@ export function extractFunctionEntries(
 
     // Can't find the files. Watch will have an exception anyway. So throw one with error.
     throw new Error(
-      'Compilation failed. Please ensure you have an index file with ext .ts or .js, or have a path listed as main key in package.json'
+      `Compilation failed for function alias ${functionAlias}. Please ensure you have an index file with ext .ts or .js, or have a path listed as main key in package.json`
     );
   });
 }