Add notebooks for smatrix plugin. Some examples that currently just need polish - 2 port network (microstrip) - Dipole antenna Qiming - [x] Rectangular patch antenna - [ ] Circular path antenna Damian - [x] [Coupled line bandpass filter](https://github.com/flexcompute/tidy3d-notebooks/pull/104) - [x] [Impedance calculation from fields](https://github.com/flexcompute/tidy3d-notebooks/pull/112) - [x] Introductory tutorial on lumped ports and path integrals - [ ] Tutorial for waveport on CPW structure Maybe: - [ ] reflective array antenna