Twirl templates

Twirl is a templating language for the Play Framework. The typical extension is a compound extension .scala.html, I'm not sure how well Linguist copes with these. The out of the box support list is html, xml, txt, and javascript (https://github.com/playframework/twirl/blob/main/api/shared/src/main/scala/play/twirl/api/Formats.scala). Syntax highlighting requires merging the grammar for twirl with the target language as both are present in the template. Further complicating things are the ability to add custom templates (https://github.com/playframework/twirl/blob/main/docs/manual/working/scalaGuide/main/templates/ScalaCustomTemplateFormat.md) so technically the extension for a twirl template is simply .scala.*, but I'm not sure if linguist could cope with a wildcard or the merging of grammars required. I would be keen to make sure .scala.xhtml is supported but because this is a custom format is not likely seeing much usage itself.

## Language name
Twirl (https://github.com/playframework/twirl)

## URL of example repository
https://github.com/playframework/play-samples/blob/2.8.x/play-scala-hello-world-tutorial/app/views/tutorial.scala.html

## Most popular extensions
.scala.*
.scala.html
.scala.xml
.scala.txt

## Detected language
Whatever the second part of the compound extension is.
html
xml
txt