Allow specifying multiple, independent packages.

[dbanty]

Change the way that single-package definition works so it looks like this:

[package]
versioned_files = [...]
changelog = ""

For multiple packages, it should look like this:

[[packages]]
versioned_files = [...]
changelog = ""
name = ""  # New required field when defining multiple

The name field will be usable in a few ways:

1. When creating a GitHub release, name it " " to differentiate between releases (with notes) for different packages.
2. The tag of the release should be <name>/v<version> to avoid version tag conflicts. This is the tagging scheme supported by Go modules—as long as name is the same as directory.
3. Useful to include in logging to specify which packages are being updated, especially in dry-runs

The BumpVersion and Release steps will apply to all packages.

[dbanty]

For monorepo support to really work, this also has to go hunt and update co-dependent packages. So whenever a package is updated, Knope should go check every other registered file of the same type for dependencies that match the package name and update them. Lockfiles will probably also need updating—but lockfiles tend to have hashes which could get tricky to do without calling out to the package manager.

[dbanty]

Some design tweaks, which will avoid breaking changes for now:

1. Change packages to be an object instead of an array when multiple packages are defined. The key is the name since it's required.
2. Support the existing syntax with a deprecation warning. Add a knope --upgrade, which auto rewrites knope.toml to the new syntax.
3. The Version variable in Command will simply not work if multiple packages are defined for now. If someone has a use case for this in the future—we'll add new syntax to support it.