require with a substitution-free template string is not recognized by process_common_js_modules

I'm using the compiler with the `process_common_js` option set to `true`.

The following code works fine:

```javascript
/** @const */
const update = require( "./update.js" );
```

However, switching to a substitution-free template string breaks:

```javascript
/** @const */
const update = require( `./update.js` );
```

resulting in:

```
src/main.js:8: ERROR - variable require is undeclared
const update = require( `./update.js` );
^^^^^^^
```

The code style of the project I'm working on imposes template strings wherever syntactically possible (only object keys get a pass and can use double quotes). Of course, this does include paths in `require` statements. Sadly, it seems the CommonJS machinery does not recognize such statements as processable.

As a workaround, I can break from the code style but it is clearly not ideal and it would be really nice if the compiler was able to handle this.