[T] Add three point bending test notebook

ProcessLib/PhaseField/Tests.cmake

Tests/Data/PhaseField/tpb_jupyter_notebook/TPB.gml

Tests/Data/PhaseField/tpb_jupyter_notebook/TPB.ipynb

Tests/Data/PhaseField/tpb_jupyter_notebook/TPB.prj

Tests/Data/PhaseField/tpb_jupyter_notebook/TPB.vtu

...s/Data/PhaseField/tpb_jupyter_notebook/figures/F_vs_u.png

...ata/PhaseField/tpb_jupyter_notebook/figures/TPB_model.png

...haseField/tpb_jupyter_notebook/figures/TPB_pf_profile.png

..._jupyter_notebook/figures/experiment_data_lower_limit.csv

..._jupyter_notebook/figures/experiment_data_upper_limit.csv

web/content/docs/benchmarks/phase-field/pf_tpb/TPB_exp.png

...cs/benchmarks/phase-field/pf_tpb/VPF_ME1_NF_CMOD_comp.png

...ntent/docs/benchmarks/phase-field/pf_tpb/VPF_ME1_frac.png

web/content/docs/benchmarks/phase-field/pf_tpb/index.md