Set maximum length of knowledge input

index.html

@@ -459,7 +459,7 @@
     </svg>
 
     <form id="knowledge-form">
-        <input type="text" id="knowledge-input">
+        <input type="text" id="knowledge-input" maxlength="50">
         <input type="submit" value="Submit" onclick="event.preventDefault(); addKnowledgeItem();">
     </form>