feat: add luarocks bin directory to the Neovim path

[vhyrro]

This PR allows any plugin running under a Neovim instance with rocks.nvim to gain access to whatever binaries are installed under .local/share/nvim/rocks/bin/. This may come in super handy for rocks which publish binaries (wink wink) :)

[github-actions]

Review Checklist

Does this PR follow the Contribution Guidelines? Following is a partial checklist:

Proper conventional commit scoping:

• For example, fix(installer): some installer bugfix

• Pull request title has the appropriate conventional commit prefix.

If applicable:

• Tested
  • Tests have been added.
  • Tested manually (steps in PR description).
• Updated documentation.

[vhyrro]

I found the end of config.lua to the best place to put the path expansion logic. Two questions:

• We should probably prepend the bin path instead of append to give it a higher priority, right? Done that.
• Should I move it from config.lua to somewhere else?

(cc @mrcjkb)

[vhyrro]

Nevermind, for some reason I thought Windows also uses : as its path separator. It actually uses a semicolon - thanks, windows.

[vhyrro]

Added hisham's very recent sysdetect rock to rocks. This will ensure that we're using the correct path separator everywhere hopefully :)

[vhyrro]

Hmm...

[mrcjkb]

Hmm...

The nix build is sandboxed. We'll probably have to package sysdetect and add it to the nix build inputs.
I'll look into it later today

[mrcjkb]

I found the end of config.lua to the best place to put the path expansion logic. Two questions:

• We should probably prepend the bin path instead of append to give it a higher priority, right? Done that.
• Should I move it from config.lua to somewhere else?

(cc @mrcjkb)

How about plugin/rocks.lua?

[vhyrro]

Fixed now!