Add a decomposition page that says hello

src/routes/decomposition.svelte

+<script lang="ts">
+    let color = "text-red-500"
+    function setColor(){ color = "text-blue-500" }
+    let valeur = 3
+</script>
+
+COUCOU
+
+<button class="block border m-2 {color}" on:click={() => setColor()}>CLIC !</button>
+<input type="number" bind:value={valeur}/>
+<p>{valeur}</p>

src/routes/index.svelte

@@ -52,6 +52,7 @@
     <li><a href="entities">Entities</a></li>
     <li><a href="parameters">Parameters</a></li>
     <li><a href="variables">Variables</a></li>
+    <li><a href="decomposition">Decomposition</a></li>
   </ul>
 
   <h2>Documentation</h2>