[mv3]: Uncaught SyntaxError: Cannot use import statement outside a module

[gurupras]

My extension is pretty large in terms of code and complexity and as a result, I have multiple files under src/background.

Currently, since I'm porting the code a little by little, I have the following:

src/background/auth.ts

import URI from 'urijs'
...

src/background/index.ts

...
import './auth'
...

After adding the import './auth' line, I end up with the following:

Uncaught SyntaxError: Cannot use import statement outside a module
Context
dist/background/index.mjs

Stack Trace
dist/background/index.mjs:16155 (anonymous function)

// src/background/auth.ts
init_esm_shims();
var import_webextension_polyfill5 = __toESM(require_browser_polyfill());
import URI from "urijs"; // <-- Highlighted line