Add RAScript language support with .rascript extension

Description

This PR adds support for the RAScript language. RAScript is a DSL that allows achievement developers for retroachievements.org the ability to design achievements using many of the modern conveniences provided by programming languages - such as variables, loops, and comments.

Checklist:

• I am adding a new language.
  • The extension of the new language is used in hundreds of repositories on GitHub.com.
    • Search results for each extension:
      • https://github.com/search?type=code&q=NOT+is%3Afork+path%3A*.rascript
  • I have included a real-world usage sample for all extensions added in this PR:
    • Sample source(s):
      • https://github.com/Jamiras/RATools/wiki
    • Sample license(s): MIT
  • I have included a syntax highlighting grammar: https://github.com/joshraphael/rascript-syntax
  • I have added a color
    • Hex value: #2C97FA
    • Rationale: The site uses two main colors, a blue and yellow, this is the blue that seems to be popular throughout each web page RGB(44, 151, 250)
  • I have updated the heuristics to distinguish my language from others using the same extension. (there are no other languages with the .rascript extension in linguist.)