Ignore styles not handled by react-native-live-markdown

[BartoszGrajdek]

Problem description

The issue is that while using live markdown input on web we're able to add styles that aren't being handled by the library. This can lead to some issues with the functionality of it.

How it should be working

The goal is to no-op any of the styles that aren't defined inside of the library, that's how it's handled on native. This means that on web there should also be some kind of function checking if the styles provided by the user are valid.

Additionally, we could throw a warning informing the user about ignored styles (on all platforms)