Always use gistId from URL for sharing, prevent duplicate gist creation (#511)

* fix: prevent duplicate gist creation

* feat: change from useEffect to loadFromGist

* Update Workspace.jsx

Author: zimiovid

src/components/Workspace.jsx

@@ -290,6 +290,7 @@ export default function WorkSpace() {
         const res = await get(shareId);
         const diagramSrc = res.data.files["share.json"].content;
         const d = JSON.parse(diagramSrc);
+        setGistId(shareId);
         setUndoStack([]);
         setRedoStack([]);
         setLoadedFromGistId(shareId);