Implement create command

[Razaloc]

Implement the create subcommand, which should create the XML .bmap format from a local image file.

[obbardc]

Tagging as wishlist since bmap-tools is fine to install in a build environment, but this feature would be nice-to-have.

[Razaloc]

quick-xml, already imported and used to read xml, can write them so it should most likely be implemented using it.