Add missing peer dependencies

[asmundg]

We require these at runtime, so they need to at least be
peerDependencies (if not normal dependencies).

Packagers such as Yarn PnP and pnpm use an unambiguous dependency
layout, where packages are only able to require their declared
dependencies. In order to consume dependencies fulfilled by our
ancestors in these scenarios, we have to declare them as
peerDependencies. This will cause the package manager to "forward"
matching dependencies declared by our parent.

[pocka]

@asmundg
I removed the peer deps once because AFAIK package user needs to install packages listed in peerDependencies on their project to suppress npm warning messages. Do Yarn PnP and pnpm support peer deps outside a dependency tree? (I'm willing to add these as direct dependencies if needed.)

[end user package]
+-- @storybook/react
|   +-- @storybook/api (can `storybook-addon-designs` use this package?)
|   +-- ...
|
+-- storybook-addon-designs

[pocka]

I'm still not sure what is the most idiomatic way to declare indirect dependencies, but I'm going to merge this since it seems using peerDependencies is the recommended way.

[pocka]

Fixed in v7.0.0-alpha.0.