Week number is highlighted when on first day of the week navigating using arrow keys

[Grisu118]

Describe the bug
Week number gets highlighted when selecting the first day of the week with arrow keys, but not when selecting any other day of the week.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://reactdatepicker.com/#example-display-week-numbers
2. Open the datepicker
3. Navigate within with the arrow keys
4. See error

Expected behavior
Either the week is always highlighted or never. The current behaviour seems to be weird

Screenshots

Desktop (please complete the following information):

• OS: Arch Linux
• Browser: Firefox / Chromium
• Version Latest

Additional context
There was already a similar issue: #4489

[OlegDev1]

We need to known in which cases the week should or shouldn't be highlighted. Could you please help with this, @martijnrusschen? Or, if possible, could you mention another contributor responsible for this?

I can work on PR for this issue and write necessary test cases.