Allow Protobuf serialized files to be opened in a text editor

[bufdev]

Given serialized.bin file, have the ability to do i.e. vim serialized.bin. Similar to gzip, vim will know to send this file to buf decode, which will use the definitions in your current directory by default, and open the file as JSON. You can edit the file, and on save, vim will call buf encode and write the file back as binary.