Plugin for markdown block

[fyliu]

Context

I have a GitHub issue template that contains a markdown block. I'd like to be able to format that block as well using mdformat.

Here's the file contents

---
name: Create Agenda
about: Assign issue to all team members day after meetup in prep for next meetup
title: ''
labels: documentation, help wanted, question
assignees: ''
---

### Overview

This issue tracks the agenda for our weekly meetings

#### Issue Template

```markdown
## [Date ]  Meeting Agenda

### Prework to prep for meeting
- [ ] #

### Recurring items: Happens on the ________ meeting
 - [ ] review any issues that are in the [new issue approval column]
 - [ ] Accountability and Support Check.
    - [ ] Review assignments for each Team member
       - [ ] [Name of Person]
- [ ] finish adding labels to the issue that are still missing them (see audit links above)
- [ ] review issues with [epic label] and define how to break down further
- [ ] Review to see if there are any members to Onboard or Offboard
      - [ ]  #

### New Items
- [ ]
- [ ] Carry over Items to next meeting that don't get addressed

### FYIs
-

### Notes from Meeting

### Task Items
```markdown

### Links to other agenda issues for your team

(so that you can easily post on their agendas items that come up at yours)

### Previous Meetings (link to each comment with the date)

Proposal

• I would like to have a plugin that will format markdown blocks. Just one level is enough I think. But maybe it's not too much extra effort to do as many levels as necessary?

• How do we know what "dialect" the markdown is in? In my example, it's gfm with a gfm block, so we assume the block is the same dialect as the parent. I don't have a good suggestion for the generic case.