`:src` type to view the source (C or Julia)

[Keluaa]

Something like @code_for :src func

Then:

• if func is a Julia function, use @less or similar
• if func is a string, assume it is an internal Julia name, and use ctags (configured for JSON output, plus caching of the tags file within a scratch dir) to find it within the Julia source (configured by the user)

In both cases, don't return a string, but rather use the pager or JULIA_EDITOR, with support for VS code.