Document how to add syntax highlighting for new file types

[johnjohndoe]

In Android Studio 4.0 Canary 8 I am currently see the following Code Style entries:

The screenshots in the README show way more Code Style entries.

Please document in the README how one get add new file types e.g. Swift.

[gaplo917]

@johnjohndoe Some languages can be installed via jetbrain plugins(Python, Go, Scala...). But, Swift is only available in AppCode.

For Swift, you have to manually import the GapStyle.jar into AppCode and then make corresponding color changes. Then follow the https://github.com/gaplo917/GapStyle/blob/master/RELEASE.md to update the color scheme.

Thank you for paying attention to this project :)

[johnjohndoe]

Thank you. I think it would be valuable to let your README point to Jetbrains documentation with regards to the points above. Users might lack experience on how to install new languages.