Added support for windows where.exe

[YourWishes]

As mentioned in #5 , Windows does not support the which command, instead using a where.exe command to replace it. I've added a new promise chain that will attempt to resolve both (which should also support WSL systems).

where.exe resolves to a series of commands where each command is on a separate line, so I've split the lines by their newline separator, trimmed the white space to remove windows systems return carriage characters before finding the first valid entry.

At the moment, for me specifically, this will result in the executable being returned before the .bat file, which is sufficient.

This does not resolve #5 but will save having to manually define the path for the time being. The theme-language-server gem itself doesn't seem to play well with Windows currently unfortunately.

[charlespwd]

Hey @YourWishes, thanks a lot for this PR! Like you said, had to do a lot of fiddling to have this work but I heavily inspired my work in #35 from this. theme-check-language-server.bat should be available in theme-check v1.2.0. It also works from the shopify-cli with shopify.bat theme language-server.

I'm closing this in favour of #35.

We should have this in prod this PM :)

Thanks again!