Emit Nix doc comments for functions

[PgBiel]

Since Nix 2.24¹², one may write :doc some-function on the Nix REPL (invoked by nix repl) to obtain a function's documentation, specified through a docstring in the format specified by Nix RFC 145³, as follows:

let
   /** Function doc */
   func = x: y: x + y;
in ...

Additionally, in Gleam, we may specify documentation comments on functions through the /// syntax, as follows:

/// Function doc
pub fn func(x: Int, y: Int) -> Int {
  x + y
}

When generating the Nix code for this function, it could be nice to translate the Gleam docstring into a Nix docstring so it can be accessed through :doc.

One concern: We'd need to escape */ in the docstring somehow. One way could be to add a whitespace between * and /, but this could be a problem depending on the contents of the docstring.

Footnotes

1. https://discourse.nixos.org/t/nix-2-24-released/49986 ↩

2. https://www.github.com/NixOS/nix/pull/11072 ↩

3. https://www.github.com/NixOS/rfcs/pull/145 ↩