Frontmatter Comments not working as expected

[oppenheimer-]

When trying to comment one or multiple lines in YAML frontmatter by pressing ctrl+# the expected result is:

---
# title: "Test Heading"
---

but it places HTML comments

---
<!-- title: "Test Heading" -->
---

[adamdehaven]

I think we could use some of the utils from the monarch-mdc > formatter-utils.ts to detect which type of block the cursor is in (e.g. YAML or non-YAML) and toggle the appropriate comment format