[feature] ignore empty rules in rules.yaml - allow trailing rule separator

[milahu]

actual result with empty rule: error: missing field id

rules.yaml

id: rule_1
language: Python
rule:
  pattern: 'aaa'
fix: 'bbb'

---

id: rule_2
language: Python
rule:
  pattern: 'ccc'
fix: 'ddd'

---

similar: trailing commas in array declarations

allowing empty rules would be useful for generating rules.yaml in a for loop

#!/usr/bin/env bash

rules_yaml=""
rule_id=0

function r() {
  rules_yaml+=$(
    echo
    echo
    echo "id: rule_$rule_id"
    echo "language: javascript"
    echo "rule:"
    echo "  pattern: '$1'"
    echo "fix: '$2'"
    echo
    echo "---" # rule separator
  )
  rule_id=$((rule_id + 1))
}

r 'nt' sleep
r 'an' firebaseApiKey
r 'on' typesenseServer

# fix: error: missing field id
rules_yaml=${rules_yaml:0: -4}

# debug: print rules yaml
echo "rules_yaml:"; echo "$rules_yaml" | grep -n ''

ast-grep scan -U -r <(echo "$rules_yaml") src/patchme.js

[HerringtonDarkholme]

After some thoughts I think this feature should be supported by serde-yaml or yaml.rs, instead of ast-grep.

Feel free to open issue there~