Move opentiny to peer dependencies

[curdopet]

What

• Moved opentiny from dependencies → peerDependencies (^6.9.0), and added it as a devDependency (^6.9.0) so the package can still build its own types.
• Changed the placeholder version from 5.1.0-rc to 0.0.0 (the real version is set from the git tag at publish time, so the committed value is meaningless).

Why

opentiny was pinned exactly (6.9.33) in dependencies. In an app that also depends on opentiny directly, a different patch version produced a duplicate, conflicting opentiny in the dependency tree. Since the wrapper uses opentiny only for TypeScript types (the editor is loaded at runtime from the window.tinymce global, never bundled), it should defer to the host app's copy.

As a peer dependency with a ^6.9.0 range, opentiny-react now binds to whatever opentiny the consuming app installs — one shared copy, no version conflicts — and we no longer need to bump this package for every opentiny patch release.