chore(flexbox): adding options to valign and halign props to handle spacing more precisely

[larprad]

General summary

It was not possible in the Flexbox component to use space-around/between/evenly css properties through props.
This PR aims to modify this by providing more options to the vAlign and hAlign props for this component.

Screenshots

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[gcornut]

Test OK
New flexbox align options work as expected ✔️