Save file option for Create Spreadsheet Button

[pydevsg]

Is your feature request related to a problem? Please describe. Whenever we try to do Create Spreadsheet+, it usually downloads a file with a default name, what if the user wants to save the file with some username in his/her desired location.

Describe the feature/solution you'd like On clicking Create Spreadsheet+ button a file dialog for the user should be opened to choose where he/she can save the file.

[pydevsg]

@IshaGupta18 , @namangupta01 what do you think? I would like to work on this issue if you kindly help me in writing the functionality, as the code is quite different from simple JS.