Flexbox docs

Updated the flexbox documentation for the current flexbox implementation

docs/objects/Flexbox/getFlexBasis.md

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+## getFlexBasis
+
+### Description
+
+The `getFlexBasis` method retrieves the initial main size of a child object within the Flexbox container. This value represents the starting point for further calculations. If the Flexbox has a direction of 'row', the flex basis is akin to the width. For 'column', it's akin to height.
+
+### Returns
+
+1. `number` The current flex basis of the object
+
+### Usage
+
+* Creates a default Flexbox, adds some objects to it, sets the flex basis for the first object, and retrieves it.
+
+```lua
+local main = basalt.createFrame()
+local flexbox = mainFrame:addFlexbox()
+local object1 = flexbox:addButton()
+object1:setFlexBasis(10) -- this object will have an initial size of 50 pixels along the main axis
+basalt.debug(object1:getFlexBasis()) -- prints: 50
+```