More examples

<a href="https://github.com/taichi-dev/taichi/blob/master/python/taichi/examples/simulation/mpm_lagrangian_forces.py"></a> <a href="https://github.com/taichi-dev/taichi/blob/master/python/taichi/examples/features/sparse/taichi_sparse.py"></a> <a href="https://github.com/taichi-dev/taichi/blob/master/python/taichi/examples/simulation/pbf2d.py"></a> <a href="https://github.com/taichi-dev/taichi/blob/master/python/taichi/examples/simulation/game_of_life.py"></a>

<a href="https://github.com/taichi-dev/taichi/blob/master/python/taichi/examples/simulation/fem128.py"></a> <a href="https://github.com/taichi-dev/taichi/blob/master/python/taichi/examples/simulation/mass_spring_3d.py"></a> <a href="https://github.com/taichi-dev/taichi/blob/master/python/taichi/examples/algorithm/mciso_advanced.py"></a> <a href="https://github.com/taichi-dev/taichi/blob/master/python/taichi/examples/simulation/mpm3d.py"></a>