Deprecated use of pkg_resources

[mh105]

1. Describe the bug
I noticed that spectrum is still using pkg_resources to manage file paths. After 3.10 there is now a warning message for deprecated API.

2. To Reproduce

• OS: any
• Python version. >3.10
• Version of spectrum: 0.8.1

Just need to import spectrum and this warning message is elicited:

DeprecationWarning: pkg_resources is deprecated as an API. See https://setuptools.pypa.io/en/latest/pkg_resources.html
    import pkg_resources

3.Expected behavior
We should switch to use importlib.resources and importlib.metadata for the same functionalities.