[gno/en] Add Gno Tutorial

[leohhhn]

Hello, we would like to add the Learn X in Y tutorial for Gno.

• I solemnly swear that this is all original content of which I am the original author
• Pull request title is prepended with [language/lang-code] (example [python/fr-fr] or [java/en])
• Pull request touches only one file (or a set of logically related files with similar changes made)
• Content changes are aimed at intermediate to experienced programmers (this is a poor format for explaining fundamental programming concepts)
• If you've changed any part of the YAML Frontmatter, make sure it is formatted according to CONTRIBUTING.md
  • Yes, I have double-checked quotes and field names!

cc @zivkovicmilos @michelleellen

[vendethiel]

you're missing the filename metadata field

[leohhhn]

Hey @vendethiel, thanks for the comment.

I wasn't fully sure what that line was for, as the repo currently contains mainly html markdown files, without any other files. Can you clarify what this adding this line would do? 🙏🏻

[vendethiel]

Sets the filename for the Get the code: button

[verhovsky]

I don't think this language should be included on Learn X in Y Minutes.