IsDirectory is not reliable. Use lfs?

[Ismoh]

NoitaMP/noita-mp/files/scripts/util/file_util.lua

Lines 252 to 255 in 8f62e6b

	function fu.IsDirectory(name)
	-- https://stackoverflow.com/a/21637809/3493998
	return (fu.Exists(name) and not fu.IsFile(name))
	end

    TestFileUtil.testIsDirectory ... 

file_util.lua | Directory nonexistingdirectory exists = false
file_util.lua | Path 'nonexistingdirectory' does not exist!
file_util.lua | Is the directory a file? nonexistingdirectory is_file = false
file_util.lua | Directory /home/runner/work/NoitaMP/NoitaMP exists = true
file_util.lua | Is the directory a file? /home/runner/work/NoitaMP/NoitaMP is_file = true
FAIL
...r/work/NoitaMP/NoitaMP/.testing/tests/file_util_test.lua:144: expected: true, actual: false
    TestFileUtil.testIsFile ... 

[Ismoh]

Fixed in #15