Add support for deployPercentage in store.publish API

[jakub-g]

The publish endpoint supports deployPercentage which could be useful for staged deploys.

[fregante]

PR welcome

[remdash]

Hello,

I am willing to make a PR for this change. I've already had a look a the code and the change looks straightforward.

There is just a design decision to make.

Most of the method to call the API have token being a last parameter and I assume this is something to keep in order to maintain consistency.

This leaves two options for the change to the publish method.

Either turning the first parameter to an object, it could look like this:

 async publish({ target = 'default', deployPercentage }, token = this.fetchToken()) {...}

Or adding a new parameter with a default value of null or undefined:

async publish(target = 'default', deployPercentage = null , token = this.fetchToken()) {...}

I can make a first version of the PR based on the first option, let me know if you prefer the second one.

[remdash]

Here is the PR: #91

[fregante]

There's actually a PR open here with the answer to that in my review: #90