feat(main.py): Add multiple iteration functionality and results summary and graph

[williamjsobczak]

Description

Add functionality that allows user to run multiple rounds of speed tests at timings of their choosing. Further, add summary results following the last speedtest and a supporting graph to visualize download speeds, upload speeds, and ping across iterations. Updated requirements.txt accordingly with associated dependencies (matplotlib).

Dependencies

Matplotlib - see requirements.txt

Future Improvements

A means to save past tests locally and re-access later may be a worthy inclusion.

Screenshots of relevant screens

[github-actions[bot]]

PR is not linked to any issue, please make the corresponding changes in the body.