[FEAT] support for listing rum package count

### Description

I would like to see the ability for fastfetch to count packages installed with rum. Rum is RakuOS's new rpm based package manager. Here's the thing, rum is able to separate "base" and "overlay". fastfetch should have the ability to count packages. Also, `rpm -qa` only lists base packages and not user packages on RakuOS.

### Motivation

Well, this isn't just for me and that's it. It is for an entirely new package manager (uses rpm package format) that is used for RakuOS which has an overlayfs mount on /usr so there is the atomic base where you can install any rpm on the overlay.

### Additional context

Using the command `rum list` will list all user installed packages. `rpm -qa` only lists base packages and when I run `rpm -qa | count` and `rum list --base | count` the package count is only off by 6 packages (rpm -qa lists slightly more for some reason) while non of the packages installed by the user are listed unless `rum list` is used and when I type `rum list | count` I have 471 packages installed.

Edit: It may be better to use `rpm --dbpath /var/lib/rakuos/rum-rpmdb -qa | wc -l` since it is faster. Maybe it can be listed as "rpm (base)" and "rpm (overlay)" for the lable kind of like how there is "flatpak (system)" and "flatpak (user)"