bug: github handler doesn't handle `org/repo#issue`

[aarondill]

Opening a github url like org/repo#issue instead tries to open the current git remote URL (and fails due to #45). for example:

> git remote -v
origin  https://github.com/sindrets/diffview.nvim.git (fetch) [blob:none]
origin  https://github.com/sindrets/diffview.nvim.git (push)

pressing gx on neovim/neovim#23943 results in the choice between searching the string or opening https://github.com/sindrets/diffview.nvim.git (fetch)/issues/23943

Instead, this should open https://github.com/neovim/neovim/issues/23943

[sportshead]

Fixed in #46

[aarondill]

@sportshead @chrishrb I've tested this with the latest HEAD(4136a82a48e8601fe8f2fde5d2ac2d706ac6d0b6) with both of these:

chrishrb/gx.nvim#46
neovim/neovim#23943

the first results in a choice between opening https://chrishrb/gx.nvim# and a google search. The second results in an error gx.nvim: No remote git repository found! and a google search.

1. Test with mkdir .repro && cd "$_" && git init && touch file && nvim file
2. paste the above contents
3. For each line:
   1. Highlight the line with V OR 0v$
   2. Press gx to open the link
   3. Observe incorrect behavior
4. Clean up the repro with rm -f file && rm -rf .git && cd .. && rmdir .repro

[sportshead]

@aarondill - thanks for the testing!

The first issue is a problem with the matching regex that doesn't include the . character while searching. The second also is that the plugin cannot find a remote. However, I can make it fallback to use github.com in the case that no repo is found but both owner and repo are passed.