Add `crdt-switch-to-buffer`

First of all, thanks for all of the work you've put into this package. I use it in my workflow to collaborate with my teammates and pair program.

@jming422 and I are working on getting crdt.el into Doom Emacs, and we wanted to add some extra functionality to crdt.el that we think will be useful for users.

The new interactive function crdt-switch-to-buffer utilizes completing-read to allow for easily and quickly switching between shared buffers.

We wanted a way to be able to switch between shared buffers in the current session without having to visit the dedicated "Buffer List" buffer. This makes switching between buffers a single step rather than a two step process.

Looking forward to hearing your feedback. Thanks!