Revise tutorial title for clarity. Add new tutorial image

Author: nikoscham

assets/HeatConduction1DWall.png

@@ -155,7 +155,7 @@ <h2 id="tutorials"><a name="Tutorials"></a>Tutorials</h2>
     <p>Below you can explore tutorials which serve as a step-by-step introduction to FEAScript:</p>
     <ul>
       <li>
-        Heat conduction in a large plane wall
+        Heat conduction through wall
         <i
           ><a href="https://github.com/FEAScript/FEAScript-core/issues/4" target="_blank"
             >(under development)</a

assets/HeatConduction1DWall.svg

@@ -91,7 +91,7 @@ <h1>Heat Flow Through a Wall</h1>
 
     <h2 id="mathematicalformulation"><a name="Mathematical formulation"></a>Mathematical Formulation</h2>
     <p>
-      <!-- ... -->
+      <img src="../assets/HeatConduction1DWall.png" width="150" />
     </p>
 
     <h2 id="solvingwithfeascript"><a name="Solving with FEAScript"></a>Solving with FEAScript</h2>