Fixed typo in using-custom-fonts.md (#10208)
Fixed typo in using-custom-fonts.md (#10208)

There should be `Font.loadAsync` instead of `Font.loadAysnc`
exponentjs/exponent,exponentjs/exponent,exponentjs/exponent,exponentjs/exponent,exponent/exponent,exponent/exponent,exponentjs/exponent,exponent/exponent,exponentjs/exponent,exponent/exponent,exponent/exponent,exponentjs/exponent,exponentjs/exponent,exponentjs/exponent,exponent/exponent,exponent/exponent,exponent/exponent,exponent/exponent