ref: Build to ESM for tree shaking

[spalmurray-codecov]

This PR changes updates our webpack config to use ESM instead of CJS modules so we can actually do tree shaking. The reason for this is our extension failed Chrome's review process due to some third party script loading code from the Sentry SDK. We don't actually use this code and it should be removed from our bundle with tree shaking.

[codecov]

Bundle Report

Changes will decrease total bundle size by 688.18kB (-52.0%) ⬇️. This is within the configured threshold ✅

Detailed changes

Bundle name	Size	Change
codecov-browser-extension-array-push	635.29kB	-688.18kB (-52.0%) ⬇️

Affected Assets, Files, and Routes:

view changes for bundle: codecov-browser-extension-array-push

Assets Changed:

Asset Name	Size Change	Total Size	Change (%)
vendor.js	-362.48kB	380.95kB	-48.76%
background.js	-319.78kB	197.59kB	-61.81%
popup.js	-2.5kB	25.91kB	-8.79%
githubFile.js	-1.99kB	9.92kB	-16.71%
githubPR.js	-1.44kB	5.21kB	-21.61%

Files in vendor.js:

• ./src/content/github/common/constants.ts → Total Size: 472 bytes

[ajay-sentry]

looks good!