Add an informatory toast to Export Tasks

[its-me-abhishek]

Is your feature request related to a problem? Please describe.
Currently if we try to export or download an empty list of tasks, the download fails silently, doing nothing except for a console warning.

Describe the solution you'd like
Add an informatory toast, preferably one line long, saying that the user does not have any task in their list, so as to export

Additional context

[Eshaan-byte]

Hey, @its-me-abhishek can you assign me. Thank you!

[harshtiwari2022]

@its-me-abhishek
I’m interested in implementing the toast notification for exporting an empty task list.
Could you please assign this issue to me so I can start working on it?