[WIP] Support for multiple release branches/channels

[craigsketchley]

Pull Request

Related issue

24

Description

Support for channels and release branches which is currently in beta in semantic-release.

Why

Multiple release branches will eventually land in master so we'll need to account for it at some point.

How

I've currently just added the option to pass an object to the extensionId config property. This is a map from release channel to extension ID.

How has this been tested

No tests as of yet.

Type of change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• [ ] Documentation
• [ ] Ready to be merged
• [ ] My code follows the code style of this project (run npm run ci to be sure).
• [ ] I have read the CONTRIBUTING document.