Add libhandy depenedency to Arch install

[SomeAspy]

Script will not run without libhandy installed, so this PR adds that to the readme

❯ python3 main.py
Traceback (most recent call last):
  File "/home/aiden/Documents/repos/SideServer-for-Linux/main.py", line 16, in <module>
    gi.require_version("Handy", "1")
  File "/usr/lib/python3.12/site-packages/gi/__init__.py", line 122, in require_version
    raise ValueError('Namespace %s not available' % namespace)
ValueError: Namespace Handy not available

I promise I'm not contribution farming 🙃

[polymo1]

I'll let someone with more knowledge on sideserver merge this. But just FYI we recommend AltCon (https://docs.sidestore.io) for sidestore installation on linux. SideServer (at least windows and mac) is currently nonfunctional.

[Spidy123222]

SideServer (at least windows and mac) is currently nonfunctional.

If I’m not mistaken. Nythepegasus fixed it on the app side to make it not have a problem. I don’t have a arch install to test this unfortunately.

[polymo1]

If I’m not mistaken. Nythepegasus fixed it on the app side to make it not have a problem.

Whoops, that's right. My bad, brain was in a billion places at once.