refactor(os): Install paru-bin instead of paru (#21)

We straight up install paru-bi via its PKGBUILD from
AUR, we skip the additional step we used to do
where we first installed paru from its GitHub
project. This saves time and most importantly
scarce RAM that Rust otherwise needs during
paru compilation.

On systems with little RAM (as in 4 GiB) paru's
compilation process would sometimes fail when
/etc/makepkg.conf when its MAKEFLAGS was
set to use many cores e.g. via "-j$(nproc --ignore 1)".

Without the manual paru compilation step we now
don't need the ability anymore to
--replace-conflicting packages.

README.md

@@ -320,7 +320,7 @@ After installation you're going to want to at least touch these points in your n
 - Unless you had a settings file or exported shell env vars per [Passwords](#passwords) you're going to want to change passwords now:
     - ZFS: The password for all datasets underneath `zpool` is `password`.
     - Local `root` account: The local `root` account's password is `password`.
-- Arch User Repository (AUR) helper: We installed [paru](https://github.com/Morganamilo/paru) as our AUR helper, we installed from GitHub via `makepkg -si` then replaced it with its [paru-bin](https://aur.archlinux.org/packages/paru-bin) version from AUR.
+- Arch User Repository (AUR) helper: We installed [paru](https://github.com/Morganamilo/paru) as our AUR helper, we installed from AUR as [paru-bin](https://aur.archlinux.org/packages/paru-bin).
 - In `/etc/systemd/network/50-wired.network` instead of a DHCP-based network config you can get a static one. The DHCP-based one for reference looks like:
     ```
     ...