feat: detect and warn if running as root

config.example.toml

@@ -6,6 +6,13 @@
 
 
 [misc]
+# On Unix systems, Topgrade should not be run as root, it
+# will run commands with sudo or equivalent where needed.
+# Set this to true to suppress the warning and confirmation
+# prompt if Topgrade detects it is being run as root.
+# (default: false)
+# allow_root = false
+
 # Run `sudo -v` to cache credentials at the start of the run
 # This avoids a blocking password prompt in the middle of an unattended run
 # (default: false)