Missing allow_branch metadata option

[Dragonrun1]

Background:
So with all the current concern with projects being being more inclusive the idea that the master branch should be named something other than 'master' has been coming up a lot. I decided on a new project to go ahead and make the change and use 'dev' since that what it used for.

Issue:
My new project is going to use workspace so I want to use cargo-workspaces with it but it seems to not work and gives me an error when I try to bump the version.
cargo ws version --amend patch
error: not allowed to run on branch dev because it doesn't match pattern master

After looking at the help a little it seems there is a --allow-branch option on the version command but having to use it every time is not really user friendly. It would be nice to be able to use something like this in Cargo.toml:

[package.metadata.workspaces]
allow_branch = "dev"

It actually would be nice to have some of the other options/arguments be available in metadata as well like bump etc.

[pksunkara]

I am a bit busy with other projects right now but I am willing to accept PRs for this.