Flexbox docs

Updated the flexbox documentation for the current flexbox implementation

docs/objects/Flexbox/setFlexBasis.md

@@ -0,0 +1,24 @@
+## setFlexBasis
+
+### Description
+
+The `setFlexBasis` method sets 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.
+
+### Parameters
+
+1. `number` Flex basis. Currently only numbers available.
+
+### Returns
+
+1. `object` The object in use
+
+### Usage
+
+* Creates a default Flexbox, adds some objects to it, and sets the flex basis for the first object.
+
+```lua
+local main = basalt.createFrame()
+local flexbox = mainFrame:addFlexbox()
+local object1 = flexbox:addButton()
+object1:setFlexBasis(10) -- this object will have an initial size of 10 pixels along the main axis
+```