Added a bevy feature to kayak_ui. 

Updated to the 0.6 release of bevy. Fixed some bugs.

TextBox text style improvements

Update bevy

* Use colour style for the text
* Use gray colour for the placeholder text
* Add more color constant

Add: `Fold` widget

Added `use_effect` hook macro

Added Provider/Consumer system

Moved logic back into use_state

Currently demonstrates the use_state and use_effect hook macros

Created a system for defining side-effects for state updates

Re-implemented event system