Documentation for v0.1 version (#199)

* Adding Equations, solving typos
* improve _code.rst
* the team rst and restuctore index.rst
* fixing errors

---------

Co-authored-by: Dario Coscia <dariocoscia@dhcp-015.eduroam.sissa.it>

docs/source/_rst/tutorials/tutorial3/tutorial.rst

@@ -25,13 +25,14 @@ The problem definition
 
 The problem is written in the following form:
 
-:raw-latex:`\begin{equation}
-\begin{cases}
-\Delta u(x,y,t) = \frac{\partial^2}{\partial t^2} u(x,y,t) \quad \text{in } D, \\\\
-u(x, y, t=0) = \sin(\pi x)\sin(\pi y), \\\\
-u(x, y, t) = 0 \quad \text{on } \Gamma_1 \cup \Gamma_2 \cup \Gamma_3 \cup \Gamma_4,
-\end{cases}
-\end{equation}`
+.. math::
+    \begin{equation}
+    \begin{cases}
+    \Delta u(x,y,t) = \frac{\partial^2}{\partial t^2} u(x,y,t) \quad \text{in } D, \\\\
+    u(x, y, t=0) = \sin(\pi x)\sin(\pi y), \\\\
+    u(x, y, t) = 0 \quad \text{on } \Gamma_1 \cup \Gamma_2 \cup \Gamma_3 \cup \Gamma_4,
+    \end{cases}
+    \end{equation}
 
 where :math:`D` is a square domain :math:`[0,1]^2`, and
 :math:`\Gamma_i`, with :math:`i=1,...,4`, are the boundaries of the