Complete archiso profile for OrionOS ISO build

- iso/profile/profiledef.sh: archiso profile with BIOS+UEFI bootmodes
- iso/profile/packages.x86_64: full package list (X11, audio, OrionOS deps)
- iso/profile/pacman.conf: pacman config for archiso
- iso/profile/airootfs/: live overlay (xinitrc, hostname, skel)
- iso/docker/Dockerfile: builds OrionOS from source, installs into airootfs, runs mkarchiso

iso/profile/pacman.conf

@@ -0,0 +1,14 @@
+[options]
+HoldPkg     = pacman glibc
+Architecture = auto
+CheckSpace
+ParallelDownloads = 5
+
+[core]
+Include = /etc/pacman.d/mirrorlist
+
+[extra]
+Include = /etc/pacman.d/mirrorlist
+
+[multilib]
+Include = /etc/pacman.d/mirrorlist