AUR SSH Host, Submodule Updates, and Manga Config & Backups

- Update `doom-emacs` submodule
- Add PKGBUILD mode to DOOM Emacs config
- Add mangal configuration to dotfiles
- Add `Manga` folder to rsync backup scripts
- Add SSH Host for AUR

.ssh/config

@@ -1,3 +1,8 @@
+# Arch User Repository (AUR)
+Host aur.archlinux.org
+  IdentityFile ~/.ssh/aur
+  User aur
+
 # CAEN On-Campus
 Host caen-oncampus
   HostName oncampus-course.engin.umich.edu