Introduce the `radicle-core` crate for housing data types that are at
the core of the Radicle protocol. The initial data type being added is
`RepoId`. To make the crate as lightweight as possible many of
dependencies are optional and gated by feature flags.
The crate is marked as `no_std` even though it unconditionally depends
on `radicle-crypto`, which is *not* `no_std`. This is to invite
refactoring of `radicle-crypto` to `no_std` at a later time.
The upgrade of the `radicle-crypto` crate was missed when upgrading
semver versions.
Unfortunately, since it is at the base of the dependency tree, all
crates that depend on it require an additional upgrade.
Fintan Halpenny
Yaroslav Halchenko
Lorenz Leutgeb