customRules method
This fuction let us add new rules as we wants. We can clear the default rules, or just write our rules. You can check html2md documentation about here: https://github.com/jarontai/html2md
Implementation
void customRules(List<hm2.Rule> customRules,
{bool clearDefaultRules = false}) {
if (clearDefaultRules) _rules.clear();
_rules.addAll(customRules);
}