Fix ESLint Not Linting Source Files

[threeal]

This issue highlights a problem where ESLint does not lint the source files because it uses the .mjs extension. This issue can be replicated by running the DEBUG=eslint:cli-engine yarn lint command, which will output the following:

As shown, only the package.json file is processed by ESLint. To resolve this issue, it is suggested to configure ESLint to parse the .mjs files.