Added Windows paths support when requiring local files

[ganigeorgiev]

This PR adds a OS dependent absolute path check when requiring local files in order to support Windows absolute paths (eg. C:\...).

Couple notes:

• I'm not sure actually if this should be allowed because the node file modules docs doesn't mention explicitly whether Windows abs path are resolvable or not (or at least I couldn't find).
  I've tested with Windows 10 VM and Node 18 and require("C:\\...") works there.

• I'm not sure whether the OS specific separators for ./ and ../ should also be added.

Edit: for more context, this was reported in pocketbase/pocketbase#3163.

[dop251]

The way the documentation is written specifically says it shouldn't work. From the portability point of view it would make sense to claim that the argument to require() is a module path, not a file path and so should always contain forward slashes regardless of the OS (as stated here). Unfortunately this does not work well with absolute Windows paths, so I guess the issue above was 'fixed' at some point, but it was not reflected on the documentation.

I don't mind using filepath.IsAbs(), as for the \. and ..\, I think they should be added, but only for Windows.

[ganigeorgiev]

I've added checks for .\ and ..\ and updated the test.