implemented creation of successor document

Signed-off-by: Stephan Richter <s.richter@srsoftware.de>

frontend/src/routes/document/View.svelte

@@ -56,8 +56,21 @@
         }
     }
 
-    function createSuccessorDoc(type){
-        console.log(type);
+    async function createSuccessorDoc(type){
+        const url = api(`document/${id}/clone`);
+        const res = await fetch(url,{
+            credentials :'include',
+            method      : 'POST',
+            body        : type
+        });
+        if (res.ok) {
+            error = null;
+            let json = await res.json();
+            router.navigate(`/document/${json.id}/view`);
+            loadDoc();
+        } else {
+            error = await res.text();
+        }
     }
 
     async function loadDoc(){