Typo fix

Author: jtpio

docs/source/examples/Widget Custom.ipynb

@@ -127,7 +127,7 @@
     "# link your development version of the extension with JupyterLab\n",
     "jupyter labextension develop . --overwrite\n",
     "\n",
-    "# rebuild extension Typescript source after making changes\n",
+    "# rebuild extension TypeScript source after making changes\n",
     "yarn run build\n",
     "```\n",
     "\n",