Validate file on save or as a seperate command

[raspi]

You can validate the rule file with nft -c -f /path/to/rules.nft which doesn't commit the rules, only checks.
So maybe add validation option to extension configuration JSON file? Something like {"checkOnSave": true}.
Extra bonus: capture the stdout/stderr of that command and if the rules are not valid, go to the offending line in VSCode.