Add Aleo Language syntax highlighting and file extension detection

[dev-sptg]

Description

Aleo is a programming language for the Aleo Virtual Machine (AVM).
With aleo language developers can create, compile and run programs on Aleo Network.
Full list of AVM opcodes https://github.com/AleoHQ/ARCs/blob/master/arc-0002/README.md
Here is the main repository: https://github.com/AleoHQ/aleo

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?utf8=%E2%9C%93&type=Code&ref=searchresults&q=extension%3Aaleo
  • I have included a real-world usage sample for all extensions added in this PR:
    • Sample source(s):
      • https://github.com/AleoHQ/aleo/tree/testnet3/examples
    • Sample license(s):
      • https://github.com/AleoHQ/aleo-instructions-syntax/blob/main/LICENSE
  • I have included a syntax highlighting grammar: https://github.com/AleoHQ/aleo-instructions-syntax
  • I have updated the heuristics to distinguish my language from others using the same extension.

[lildude]

There are only 15 .aleo files on GitHub. This is a long long long way away from our documented minimum requirements and even our temporarily relaxed requirements. Closing this but please feel free to re-open when usage has grown.