chore(stylex,tests): bump stylex to 0.6.0 and fix tests

[kelset]

Following up from the release of stylex 0.6.0: https://github.com/facebook/stylex/commit/87e718e6f07359a5e7cfce59da6ea89f70917bed

This PR also takes care of fixing npm run test. It was originally failing because mime-types was not a direct dependencies, and then snapshots needed to be updated.

I also tested the examples, as far as I can tell it's working:

It throws an error in logs saying:

Warning: Failed prop type: Invalid prop `position` of value `static` supplied to `Text`, expected one of ["absolute","relative"].`

so probably it was something pre-existing.

[necolas]

Thanks