feat: add support to follow links in markdown format

[pbogut]

Currently this plugin supports links in wiki format like this:

[[some/file.md|My file]]

but markdown links looks bit different

[My file](some/file.md)

This PR will add support for markdown links to ObsidianFollowLink command as well as utils.cursor_on_markdown_link function.

[pbogut]

Here I'm changing markdown link to look like wiki link. I think that will be better for compatibility. If someone has custom note_id_func it will still work nicely with markdown links.

[epwalsh]

Hey @pbogut, this looks good overall, but I just noticed one issue. If you have a markdown link that's actually a URL, :ObsidianFollowLink will try to create a note based on that URL. That's not ideal. One way we could handle this is to not create notes when the link is markdown style as opposed to Wiki style. Open to other suggestions as well. I just think that URL detection can be tricky.

[pbogut]

If you have a markdown link that's actually a URL, :ObsidianFollowLink will try to create a note based on that URL.

Isn't that an issue already? I mean, isn't [[https://example.com|My Example]] valid wikilink?
Anyway, maybe we could look for ^[a-z0-9]*%:%/%/ ^[%a%d]*%:%/%/ and if that matches we consider it a link (let it be http://, file://, ftp:// or otherwise) and ignore? I guess we can either ignore it or pass it through to the system to open it.
I don't want to mess with that, especially because I'm only using one OS, but maybe I could add an option where user could set up their own system command that should be run for links and by default they would be ignored?

So my questions:

1. Is matching against ^[a-z0-9]*%:%/%/ ^[%a%d]*%:%/%/ acceptable for you to detect URI's?
2. Can I add an option to run some command when link is detected?
   It would be something like:

require("obsidian").setup({
  url_handle_cmd = "gio open {}",
})

-- Edit:

Or even better, add hook instead:

require("obsidian").setup({
  follow_url_func = function(url) --[[ do what you fancy ]] end,
})

[epwalsh]

Isn't that an issue already? I mean, isn't [[https://example.com|My Example]] valid wikilink?

I suppose you're right. We should probably handle URLs better at some point, but that seems out-of-scope for this PR.

[epwalsh]

LGTM! Thanks @pbogut :)