Feature/delegate to first font in fallback list on React Native

[Jta26]

In working with some internal stuff, I needed to do a pretty gnarly code-split between Web, Android, and iOS due to different platforms having different names for their fonts. In addition, I needed to do !important on web to override a bunch of high specificity styles in a global CSS file. When I added !important, I noticed the incompatibility here.

!important is being sent down through an html.span to the underlying <Text>'s TextStyleProps in RN, resulting in an undefined font family. RSD will also send down fallback fonts, also resulting in undefined fonts. Ideally !important is never used in atomic styles, but in the event that it is used, I think it's reasonable to strip it off completely.

Example:

Thought I'd try to throw up a PR that fixes it.

Two Questions

1. Should we change this to always strip off !important for all CSS properties? There is no value in doing anything with !important on native imo.
2. Is delegating to the first font in the list of fallbacks the right thing to do here? Should we do a runtime check on font's somehow to support proper fallbacks?

Snapshot tests written by AI

[Jta26]

Synced offline, updated this PR to not do anything with !important, but it will still handle delegating to the first font in the list of fallbacks on React Native.

[meta-cla]

Hi @Jta26!

Thank you for your pull request.

We require contributors to sign our Contributor License Agreement, and yours needs attention.

You currently have a record in our system, but the CLA is no longer valid, and will need to be resubmitted.

Process

In order for us to review and merge your suggested changes, please sign at https://code.facebook.com/cla. If you are contributing on behalf of someone else (eg your employer), the individual CLA may not be sufficient and your employer may need to sign the corporate CLA.

Once the CLA is signed, our tooling will perform checks and validations. Afterwards, the pull request will be tagged with CLA signed. The tagging process may take up to 1 hour after signing. Please give it that time before contacting us about it.

If you have received this in error or have any questions, please contact us at cla@meta.com. Thanks!