doc: update

README.md

@@ -95,13 +95,10 @@ Suppose you want to solve for the orbit of an interplanetary vehicle (that is
 Sun is the main attractor) form which you know that the initial and final
 positions are given by:
 
-$$
-\vec{r_1} = \begin{bmatrix} 0.159321004 \\ 0.579266185 \\ 0.052359607 \end{bmatrix} \text{ [AU]}
-$$
-
-$$
+```math
+\vec{r_1} = \begin{bmatrix} 0.159321004 \\ 0.579266185 \\ 0.052359607 \end{bmatrix} \text{ [AU]} \quad \quad
 \vec{r_2} = \begin{bmatrix} 0.057594337 \\ 0.605750797 \\ 0.068345246 \end{bmatrix} \text{ [AU] }
-$$
+```
 
 The time of flight is $\Delta t = 0.010794065 \text{[year]}$. The orbit is
 prograde and direct, thus $M=0$. Remember that when $M=0$, there is only one