Replace deprecated pkg_resources with importlib

[arthurbdiniz]

Problem

pkg_resources has been removed from Setuptools 72.0.0+ (see setuptools#3085), causing import errors in environments with newer Setuptools versions.

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Solution

This PR replaces the deprecated pkg_resources.resource_filename with the modern standard library alternative importlib.resources.files, which is the recommended approach for accessing package resources.

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Changes

• Removed pkg_resources import
• Added importlib.resources.files with fallback to importlib_resources for Python < 3.9
• Updated resource file access to use the new API:
  • files('activipy').joinpath('activitystreams2-context.jsonld')
  • .read_text() instead of open().read()

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Compatibility

• Python 3.9+: Uses built-in importlib.resources
• Python < 3.9: Falls back to importlib_resources package (needs to be added as a dependency)

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Testing

Existing tests pass with the new implementation.

The change is a drop-in replacement with no functional differences.

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Note

Projects using this library with Python < 3.9 will need to install importlib_resources as a dependency.