typed signatures in documentation

[baggepinnen]

I would find it useful to have type restrictions reflected in the method signatures shown in the documentation. When I read

attach!(mechanism, predecessor, successor, joint; joint_pose, successor_pose)

I'm finding it hard to know what types are expected for all arguments. Something like

attach!(mechanism::Mechanism, predecessor::RigidBody, successor::RigidBody, joint::Joint;  joint_pose::Transform3D,
        successor_pose::Transform3D)

would certainly help.

Since this package is already using DocStringExtensions, perhaps this could be accomplished by simply changing

$(SIGNATURES)

to

$(TYPEDSIGNATURES)

https://juliadocs.github.io/DocStringExtensions.jl/latest/#DocStringExtensions.TYPEDSIGNATURES