Convert system state space equations to LaTeX in README

Updated mathematical representation to LaTeX format.

Author: MRGilak

README.md

@@ -54,11 +54,11 @@ An extended PFC controller is implemented to control a nonlinear system. The exe
 
 
 The system state space representation is as follows:
-```
-x1_dot = x2
-x2_dot = -0.33 * exp(-x1) * x1 - 1.1 * x2 + u
-y = x1
-```
+$$
+dot{x}_1 = x2
+\dot{x}_2 = -0.33 e^{-x_1} x_1 - 1.1 x_2 + u
+y = x_1
+$$
 
 Any other system can be used instead. It's simply a matter of system definition in one function, which will be shown later.
 A change of variables is considered as: