Add backup script

Signed-off-by: Nikolaos Karaolidis <nick@karaolidis.com>

hosts/common/configs/system/backup/backup.completion.zsh

@@ -0,0 +1,16 @@
+_backup_completion() {
+  local options=(
+    '-m[specify partition to mount for backup]:partition:($(_partitions))'
+    '-b[specify backup directory]:backup directory:_files -/'
+  )
+  local curcontext="$curcontext" state line
+  typeset -A opt_args
+
+  _partitions() {
+    lsblk -rno NAME | sed 's/^/\/dev\//'
+  }
+
+  _arguments -s $options
+}
+
+compdef _backup_completion backup