Mark buffers created from stdin as modified (#7431)

This resolves some confusing behavior where a scratch document created
by piping into hx is discarded when navigating away from that document.

We discard any scratch documents that are not modified and the original
`Editor::new_file_from_stdin` would create unmodified documents. We
refactor this function to create an empty document first and then to
apply the text from stdin as a change.

0 files changed, 0 insertions, 0 deletions