How do i convert a text file type to unity3d ignore file type?

I unchecked in the file explorer the option for Hide extensions for known file types

then in the folder itself i have a text file name Unity.gitignore.txt , the file was type gitignore i downloaded from the internet from here https://github.com/github/gitignore/blob/main/Unity.gitignore but then i edited it to change inside the content using notepad and since then the file is type text txt. and when i try to rename it i can change the file name to Unity.gitignore but the extension stay text txt type.

i can't change the extension type of the file.

The extension type is still .gitignore. If you mean that Text Document type , there shouldn't be any problem with it. If you don't like it, you can delete the (default) item (its value should be txtfile) from the HKEY_CLASSES_ROOT\.gitignore path in the registry, and then restart the explorer.