Allow multiple point selection with shift key

[JustinElms]

Background

The OpenLayers select feature inherently allows users to select multiple features by holding the shift key when clicking on them. The Map component however fires the signal to open the plot window immediately after a selection is made preventing users from easily selecting multiple points to plot. A shift key check is added to the select function to signal that the user is selecting multiple points prevents the window from opening via a multiSelect state variable. Likewise, an event listener is added to the main ocean navigator component to check that the shift key is released which modifies the multiSelect state and allows the plot window to open.

Why did you take this approach?

These checks allow the navigator to track when the user is selecting multiple points and delay the opening of the plot window.

Anything in particular that should be highlighted?

Multiple point selection is only enables when the user is selecting points to plot.

Checks

• I ran unit tests.
• I've tested the relevant changes from a user POV.
• I've formatted my Python code using black ..