fix: Replace use of deprecated `pkg_resources` by `importlib`

[dbaty]

pkg_resources is deprecated (https://setuptools.pypa.io/en/latest/pkg_resources.html).

Closes #65.

[sshishov]

@dbaty when we can expect this PR to be landed on the codebase?

We are receiving this warning and it would be nice to fix it... Half a year passed since the PR opened (1 file, 2 lines) and still not merged/released.

Thank you for continuous support!

Best regards, Sergei

[dbaty]

I plan to release a new version with this fix this week. Sorry for the delay.

[dbaty]

@sshishov : I have released version 3.0 today that contains this fix.