fix(rockspec): adjusted luarocks executable to contain the appropriate extension on windows

[TheZoc]

This fixes the problems with :checkhealth and package building on Windows when using luarocks. Previously it wasn't adding the correct extension, depending on the user setup.

Remarks:

1. LuaRocks has 2 different distribution packages, one that uses a .bat and another one that uses a .exe.

2. vim.fn.executable() will work if the extension is omitted, but Process.exec() will fail

This should solve most of the Windows users headaches when using LuaRocks with lazy.nvim

[github-actions[bot]]

This PR is stale because it has been open 30 days with no activity.