[PatternLang] Match Constant Nodes

Thanks for the pointer! So I’ll open a PR this afternoon including the following:

  • Add ConstantPattern
  • Add descriptions to the doc about how to match constant with or without a specific value.
  • Add description to the doc about welcome to raise an issue or open PRs to add more pattern nodes.

Meanwhile, let me know if you have any else to add :slight_smile: