Update docs

Author: lululxvi

docs/demos/pinn_forward.rst

@@ -47,6 +47,7 @@ Time-dependent PDEs
    pinn_forward/allen.cahn
    pinn_forward/klein.gordon
 
+- `Heat equation with training points resampling <https://github.com/lululxvi/deepxde/blob/master/examples/pinn_forward/heat_resample.py>`_
 - `Diffusion-reaction equation <https://github.com/lululxvi/deepxde/blob/master/examples/pinn_forward/diffusion_reaction.py>`_
 - `Beltrami flow <https://github.com/lululxvi/deepxde/blob/master/examples/pinn_forward/Beltrami_flow.py>`_
 - `Kovasznay flow <https://github.com/lululxvi/deepxde/blob/master/examples/pinn_forward/Kovasznay_flow.py>`_

docs/demos/pinn_inverse.rst

@@ -20,6 +20,7 @@ Time-independent PDEs
 
    pinn_inverse/elliptic.inverse.field
 
+- `Inverse problem for the Poisson equation with unknown forcing field with training points resampling <https://github.com/lululxvi/deepxde/blob/master/examples/pinn_inverse/elliptic_inverse_field_batch.py>`_
 - `Inverse problem for Brinkman-Forchheimer model <https://github.com/lululxvi/deepxde/blob/master/examples/pinn_inverse/brinkman_forchheimer.py>`_
 - `Inverse problem for the diffusion-reaction system with a space-dependent reaction rate <https://github.com/lululxvi/deepxde/blob/master/examples/pinn_inverse/diffusion_reaction_rate.py>`_