Add date range and footer to widget

[ckcherry23]

What feature(s) would you like to see in RepoSense

Add more relevant information to the widget such as:

• Date range of the chart
• Attribution to RepoSense in the Footer

Is the feature request related to a problem?

Currently, this is how the widget UI looks. We can add more relevant information to make the ramp/bar charts more meaningful and link back to the RepoSense website.

Additional notes

This issue may involve some UI design as well.
For the footer, we can refer to the current footer of the full RepoSense web report for consistency in design.

[ckcherry23]

Considering that the new optimize/trim timelines feature from #2180 shows the optimised date range at the bottom left/right of the ramp chart, this code can be reused to show the date range for widgets.