Provide a Reader::from_read interface

[RoloEdits]

As far as I can see, the only API for getting a Reader is using from_str and new, both of which take a &str.

Having something like:

Reader::from_read<R: Read>(read: R)

would make it simple to pass in a File, for example, without glue code to get a &str or bytes, and passing it to the current interface.

[bluk]

It would be a nice convenience method. One issue is that the parser doesn't own the underlying string, so perhaps a new type would need to be created that owns the bytes and the current position.

For my use cases, I use memmap2 or am reading from a database which is why I borrow the bytes.