Is there a particular reason that pulldown-cmark defines its own type, StrWrite, rather than using the built-in Rust trait core::fmt::Write? Previously core::fmt::Write's documentation said

This trait should generally not be implemented by consumers of the standard library.

But in a recent PR, I changed it to remove that section since no one knew of a reason why it said that. Perhaps it would be good to move pulldown over to that built-in trait?