Add ast-grep for Language Agnostic

[StevenLove]

Information:

Language: Agnostic
Linter: ast-grep
URL: - https://ast-grep.github.io
Checklist:

• Only added one linter?
• Is it inside the right language container?
• Is it sorted alphabetically inside the container?
• Does the title follow the template: "Add [LINTER] for [LANGUAGE]."?
  For reference, there's some contributing guidelines.