recommonmark internal links + move to myst-parser?

[jgoeders]

I'm having issues creating internal documentation links. We are using recommonmark to support markdown files in our sphinx documentation (which is nice), and recommonmark is supposed to support internal links, but I can't get it to work.

For example, if I have a link like:

[Get VTR](vtr/get_vtr) 

The link is being converted to an external github link (https://github.com/verilog-to-routing/vtr-verilog-to-routing/blob/master/vtr/get_vtr). I think this is connected to the fix where we wanted to link to files in the root of the Github repo (#1785) but I think something is broken.

@acomodi ?

I figured we must have internal links elsewhere, but the only one I can find lives on line 202 of this page and is broken:

If unsure, there are several outlets to ask questions in the [Help](./help.md) section.

Anyone know a fix to this?

I'm also wondering if others would be interested in moving to the newer myst-parser? recommonmark is now deprecated and myst-parser is the official Sphinx markdown parser.

I would be fine with taking a crack at this if people are interested. We don't have that much markdown documentation, and recommonmark syntax is supposed to be supported, so I don't think it would be too bad to do. Also, the SymbiFlow/sphinxcontrib-markdown-symlinks fix would not be needed since including a file from outside the docs folder is supported in myst.

[jgoeders]

@acomodi @mithro
Here is the method I've come up with using myst-parser (new official Markdown processor for Sphinx) to handle all manner of links between top-level Markdown files (eg README.md) and Sphinx documentation (eg /doc/src/), whether they are included in the Sphinx build, or just being viewed on Github.

executablebooks/MyST-Parser#361 (comment)