Fedora performance fixes

[Sisyphus1813]

• This update fixes performance issues on Fedora systems that was caused by Pull Request 6.
• The performance issues revolved around using rust's Commands which are (comparatively) slow as they rely on CLI.
• This has been replaced by the rpm-pkg-count crate, which has improved performance on the Fedora kernel significantly. However, this does require installation of the rpm-devel package on Fedora systems in order to display installed package count, otherwise it will return an empty value, but will not cause runtime or compile issues.
• Updated README to reflect Fedora support and the other changes.

[charleschetty]

Thanks for your PR,

Seems that there is no suitable method to quickly count RPM packages without introducing external libraries. I checked the fastfetch, they also use librpm....

[charleschetty]

• This has been replaced by the rpm-pkg-count crate, which has improved performance on the Fedora kernel significantly. However, this does require installation of the rpm-devel package on Fedora systems in order to display installed package count, otherwise it will return an empty value, but will not cause runtime or compile issues.

I think the cargo features mechanism may help ()

[Sisyphus1813]

Cool! I will look more into this also.

Later down the line we could possibly rewrite the cargo package itself such that we aren't introducing third party dependencies. But yes, right now I also don't see a reason to reinvent the wheel. Thanks!