Add Gnolang (smart-contracts)

[moul]

This PR adds an entry for the Gnolang language.

Description

Following the directions in CONTRIBUTING.md, this PR adds:

• A language entry for Gno.
• A grammar specification for Gno.
• Sample scripts used in real world contracts.

Checklist:

• [x] I am adding a new extension to a language.

  • [x] The new extension is used in hundreds of repositories on GitHub.com
    • Search results for each extension:
      • https://github.com/search?q=path%3A*.gno+NOT+nothack&type=code Important: We have multiple contracts uploaded on-chain too. Additionally, we encourage opening PRs against the main repo instead of creating new ones. This helps expand the examples folder, enhancing the language parser and tooling.
  • [x] I have included a real-world usage sample for all extensions added in this PR:
    • Sample source(s):
      • [URL to each sample source, if applicable]
    • Sample license(s):
  • [ ] I have included a change to the heuristics to distinguish my language from others using the same extension.

• [ ] 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%3AFOOBAR+KEYWORDS+NOT+nothack
  • [ ] I have included a real-world usage sample for all extensions added in this PR:
    • Sample source(s):
      • [URL to each sample source, if applicable]
    • Sample license(s):
  • [ ] I have included a syntax highlighting grammar: [URL to grammar repo]
  • [ ] I have added a color
    • Hex value: #RRGGBB
    • Rationale:
  • [ ] I have updated the heuristics to distinguish my language from others using the same extension.

• [ ] I am fixing a misclassified language

  • [ ] I have included a new sample for the misclassified language:
    • Sample source(s):
      • [URL to each sample source, if applicable]
    • Sample license(s):
  • [ ] I have included a change to the heuristics to distinguish my language from others using the same extension.

• [ ] I am changing the source of a syntax highlighting grammar

  • Old: [URL to grammar repo]
  • New: [URL to grammar repo]

• [ ] I am updating a grammar submodule

• [ ] I am adding new or changing current functionality

  • [ ] I have added or updated the tests for the new or changed functionality.

• [ ] I am changing the color associated with a language

  • [ ] I have obtained agreement from the wider language community on this color change.
    • [URL to public discussion]
    • [Optional: URL to official branding guidelines for the language]

[lildude]

I know this is still in draft, but I've added the "Pending Popularity" label as there are only 52 files currently indexed if we exclude the gnolang/gno repo and all the forks of it which is a long long way from our usage requirements.