Reference links require protocol prefix

[WovenTales]

Description

I've been wanting to switch to reference links for a while, given how Vim's concealment interacts with word wrapping, but hadn't had any luck getting it to work. Reading through another issue here for a second or third time, I finally noticed that they prefixed their example path with wiki: -- and when I added that to mine, everything finally navigated properly. I had never considered that as being the issue since inline links don't require a protocol to be specified. Now that I'm aware of the limitation, I can certainly work around it, but I wonder if it wouldn't be better to allow in-wiki reference links to just name the bare path identically to in-wiki in-line links; or if there's a technical or format-based reason to enforce the difference, then the documentation should make the requirement clear (there's nothing in :help wiki-link-reference about the protocol either way).

Minimal working example

* This is a functional link: [link](wiki:target.md).
* This is as well: [link](target.md).
* This link works: [link][valid].
* This one doesn't: [link][bad].

  [valid]: wiki:target.md
  [bad]: target.md

[lervag]

I don't see any good reasons not to allow the "unprotocolled" urls for reference links. I'm making it with one minor caveat, though: If the target does not exist, then we will instead move the cursor to the recognized reference (similar to the current behaviour).

Let me know what you think!

[WovenTales]

Yeah, that looks good, thanks! Jumping down to the reference is intuitive enough, and I can certainly see how it may avoid unexpected behaviour. It's still a bit weird to jump down, W over to the link and hit enter only to have the bare path be wrapped in a link syntax rather than opening the expected page, but between that and potentially linking via something that was only intended as a footnote, I definitely appreciate the current behaviour.