Fix Jupyter React Examples

[echarles]

As reported by @MarcosVn in #341 (comment)

./src/examples/Deno -> (File Load Error for 10.2_Polar DataFrames.ipynb);
./src/examples/JupyterLabApp -> Did not load the ipynb files correctly for use;
./src/examples/JupyterLabHeadlessApp -> Did not load the ipynb files correctly for use;
./src/examples/NotebookLite -> Could not find "ping.ipynb"