Add support for Literate Juvix Markdown

[jonaprieto]

This PR adds an initial support for Literate Juvix Markdown files, files with the extension .juvix.md.

Here is a small example of such a file: Test.juvix.md.

# This is a heading
Lorem ...

```juvix
module Test;

type A := a;

fun : A -> A 
 | _ := a;
```
Other text

This initial support enables users to execute common commands such as typechecking, compilation, and HTML generation. Additionally, a new command called markdown has been introduced. This command replaces code blocks marked with the juvix attribute with their respective HTML output, much like the output we obtain when running juvix html. In this version, comments are ignored in the output, including judoc blocks.

• We intend to use this new feature in combination with this Python plugin (https://github.com/anoma/juvix-mkdocs) to enhance our documentation site.

2023-10-30.15.28.03.mp4

Future work

Open as issues once this PR is merged, we can work on the following:

• Support imports of Juvix Markdown modules (update the path resolver to support imports of Literate Markdown files)

• Support (Judoc) comments in md Juvix blocks

• Support Markdown in Judoc blocks

• Update Text editor support, vscode extension and emacs mode (the highlighting info is a few characters off in the current state)

• Closes Integration of Juvix with Mdbook for Juvix Excerpts #1839

• Closes Syntax coloring in the documentation #1719