updating DIRECTORY.md

Author: umang-dadhich

DIRECTORY.md

@@ -975,6 +975,7 @@
   * [Lorentz Transformation Four Vector](physics/lorentz_transformation_four_vector.py)
   * [Malus Law](physics/malus_law.py)
   * [Mass Energy Equivalence](physics/mass_energy_equivalence.py)
+  * [Maxwells Equations](physics/maxwells_equations.py)
   * [Mirror Formulae](physics/mirror_formulae.py)
   * [N Body Simulation](physics/n_body_simulation.py)
   * [Newtons Law Of Gravitation](physics/newtons_law_of_gravitation.py)