Defines the default size of an element before the remaining space is distributed.
The value can be a length (e.g. 20%, 5rem, etc.) or 'auto' (which means "look at my width or height property").
If set to 0, the extra space around content isn't factored in. If set to auto, the extra space is distributed based on its flex-grow value.
flex-basis: <length> | auto; /* default auto */