fix(builder): css hash incorrectly transforming data urls

[marvinhagemeister]

Fixes #2599

[csvn]

Awesome! I think this PR might fix an issue I had yet managed to look into, where some icons where rendered as ⬜. I use url() with SVG's inside CSS properties too (e.g. --icon-foo: url("data:image/svg+xml,%3Csvg ...");, similar to Icons in Pure CSS), so this looks likely to solve my issue too! 🎉