Change to be independent of the path package

[blendthink]

Issue

• [Improve]: Remove packages from dependencies in yumemi_lints #138

Overview (Required)

The path package was introduced to utilize the path.join() function.
path.join() is a function that concatenates the specified path segments into a single path using the separator of the current platform.
https://pub.dev/documentation/path/latest/path/join.html

To maintain the previous behavior, I implemented only the necessary parts manually.

Links

• https://pub.dev/packages/path
• https://pub.dev/documentation/path/latest/path/separator.html
• https://github.com/dart-lang/path/blob/e969f42ed112dd702a9453beb9df6c12ae2d3805/lib/src/style.dart#L36-L45

Screenshot

2024-09-19.8.31.54.mov

[github-actions]

Ready for review 🚀

[morikann]

I have not been able to confirm that it works in a Windows environment, but it is LGTM since there is no problem in the code!