[draft][examples] Add examples with Hermite-type bases
This adds three examples:
- 2d Poisson equation with cubic Hermite-basis and weak enforcement of Dirichlet BC (Nitsches method).
- 2d Poisson equation with cubic Hermite-basis and strong enforcement
of Dirichlet BC utilizing the
FunctionalDescriptor
interface. - 2d biharmonic equation with nonconforming Morley basis and strong
enforcement of clamped BC utilizing the
FunctionalDescriptor
interface.