Add support for 'font-kerning' in geckolib
Add support for 'font-kerning' in geckolib
These changes fix#13667
$ ./mach build -d
It looks like you passed an unrecognized argument into mach.
$ ./mach test-tidy
It looks like you are trying to run an unknown mach command: test-tidy
I'm clearly doing something wrong here, but I'm not sure what
- [x] These changes do not require tests because "[For stylo it's okay to not have tests since many of the reftests fail due to unrelated reasons](https://github.com/servo/servo/pull/13570#issuecomment-251354116)" :)
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