Provide option to add CSV, Excel, or Parquet file from Finder/files instead of just drag and drop

[cole-at-quadratic]

Currently this flow only reminds the user that they can drag and drop these types of files into Quadratic. We should add additional functionality to launch the finder when selecting the "From file (CSV, Excel, or Parquet)" option in the Insert > Data menu, and when a file is selected from finder, file is inserted starting at the currently selected cell