Add support for `x_google_ignoreList`

[bmeurer]

magic-string is used throughout various parts of the JavaScript ecosystem that deal with generating and manipulating source maps. Having basic support for the new x_google_ignoreList source map extension¹² will make it easy and natural for tools to mark library / framework code as ignore-listed (for debuggers).

Doc: https://goo.gle/devtools-ignoreList-adoption

Footnotes

1. https://developer.chrome.com/blog/devtools-better-angular-debugging ↩

2. https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k/edit#heading=h.mt2g20loc2ct ↩

[antfu]

Close as it's shipped 🎉

[bmeurer]

Only the initial support landed. As proposed in the doc, for easier adoption, a second follow up PR should land (which I'm preparing) to add support for marking sources as ignore listed when adding to bundles.