Create util file for graph default props value #82

To keep the consistency of the layout across pages, we can have a util file to contain all the graph default props value shared across graph components. This can take the same format as Color.ts to enable smart autocomplete in visual studio code.

These default graph props can include the following props:

const defaultGraphWidth = isMobile ? width / 1.25 : width / 2;
const defaultPieChartWidth = isMobile ? width / 1.25 : width / 3;
const defaultGraphHeight = 500;

const defaultBarGraphMargin = { top: 20, bottom: 80, left: 60, right: 20 };

const defaultLabelSize = 24;
const defaultLabelWidth = 100;

Note the isMobile will probably have to be passed in as a function since this value is determined in the page.