Escaped Character highlighting support inside string literals.

[EmranMR]

Hello!
This pull request adds highlighting support for escape characters. Currently Nova does not have a specific theming selector for these characters like the regex.escaped, or the string.escape that was written in objc/highlights.scm

I followed your convention of using @value.number for char values, so that the theming is consistent across.

• I have seen this in other editors and it's extremely beneficial to relieve eye strain 😵‍💫 , esp in printf style functions!
• I did the same for Objective C, swift and C.

PS. I am very new to C family programming language and barely touched the surface with C++. I gave it a shot myself in all the languages and it seem to work fine. However I found a parsing bug 🐞 while I was testing, very likely due to core Nova, Unrelated to this extension or tree-sitter 🌳 and I will raise it via the form on Nova.app. Other than that it worked as expected on my side! 😊

👇👇👇👇👇👇