Two code fences that do not contain are not marked as such, leading to
false negatives when testing `radicle-core`. To remedy, mark these
fences as text.
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.
Lorenz Leutgeb
Adrian Duke
Fintan Halpenny