Support module files with multiple H2 for grouping cmdlets

[sdwheeler]

Summary of the new feature / enhancement

Some modules support multiple feature areas. The module markdown file can group the cmdlets by feature area where each feature area is represented by an H2 with H3 entries for each cmdlet in that group. The H2 may have an optional markdown content before the first H3.

Proposed technical implementation details (optional)

Example markdown:

## Feature 1 cmdlets

Optional collection of paragraphs (or other non-Header markdown).

### [cmdlet1-name](cmdlet1-name.md)

Synopsis of cmdlet1-name

### [cmdlet2-name](cmdlet2-name.md)

Synopsis of cmdlet2-name

## Feature 2 cmdlets

### [cmdlet3-name](cmdlet3-name.md)

Synopsis of cmdlet3-name
...

Requirements

• Need to be able to import module markdown in this format
• Need to be able to re-export the imported module markdown (e.g. for conversion from v1 to v2 format)
• New-MarkdownCommandHelp -WithModulePage should output a flat module markdown file
  • Creating or updating an existing module markdown file with groupings is out of scope for this release.
• Need to be able to convert a module markdown file that has multiple H2 into Yaml

[sdwheeler]

Fixed in https://github.com/PowerShell/platyPS/commit/27d5ffe4090f146b64c7d91453d6683c68c8ee53