Feat/346 nia national 48 hours => adding datestamp to chart

[rachel-labri-tipton]

Pull Request

Description

With the 48-hour forecast, we're showing 3-4 days of data in the nowcasting charts. This adds a second x-axis with a date to the nowcasting app charts.

The updated axis looks like this:

It was tricky to get the date to look centered under the first x-axis, so would appreciate any feedback or suggestions for positioning the second x-axis under the first x-axis.

Fixes #346

How Has This Been Tested?

This has been tested by running the code locally.

Checklist:

• [x] My code follows OCF's coding style guidelines
• [x] I have performed a self-review of my own code
• [ ] I have made corresponding changes to the documentation
• [ ] I have added tests that prove my fix is effective or that my feature works
• [x] I have checked my code and corrected any misspellings

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Name	Status	Preview	Comments	Updated (UTC)
nowcasting-app	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Nov 22, 2023 5:45pm
nowcasting-website	✅ Ready (Inspect)	Visit Preview		Nov 22, 2023 5:45pm

[peterdudfield]

Thanks @rachel-labri-tipton for this, it looks good for the screen shot above. Perhaps @braddf can review the code

[rachel-labri-tipton]

The unit tests are a good idea, @peterdudfield. I'll have a look at it today.