[FR] Treat md files like jmd files

[kapple19]

The VS Code editorial experience for *.md files is much better than for *.jmd files, so I prefer to create my files with the *.md extension.

When I weave("*.md"), it doesn't run the julia codeblocks, so I have to convert my file to *.jmd when I want to weave it.

Can Weave.jl treat *.md files the same as *.jmd files and run the julia codeblocks for at least this use case?