`excluded_directories` is not taken into account when calling with file paths

[fehnomenal]

If I call gdlint or gdformat with a concrete file, like gdlint addons/guide/guide.gd it reports many errors even though I have set the addons/ directory in excluded_directories. This results in the vscode extension (https://github.com/EddieDover/vscode-formatter-godot) to report errors when browsing files that should be ignored.

In the utility function to collect *.gd files the setting is only taken into account while traversing directories and if only files get passed they are taken as they are without checks. I think the path should be checked to NOT contain any string of /<excluded_directories>/.