feat: pretty print HTML

[a-frantz]

Describe the problem or feature in addition to a link to the issues.

Update wdl-doc to pretty print HTML. Achieved via the Debug format of the html crate.

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[claymcleod]

Seems like this needs some newlines.

[claymcleod]

Let's see what the results look like when you add the newline to the print statements.