Better IE support, more robust JS components

Add check for element in JS table #71 and filter component #73
Add JS dependencies for components that use CSS custom properties and need cd-polyfill.js
Add closest polyfill #72

Component library weights, better PE for hero component, remove legacy table rules

Component library weights #68
better PE for hero component #69
remove legacy table rules #70

System font for default typography, improvements to button and table components

better typography using system fonts for body, and example webfont
#61

refine button component with modifiers for size, and style
refine table component with better wrapping anchors in cells
#64

Improve Node sidebar layout

Fixes issue #58 and reduces use of important due to no longer having to override extends

Better cross-browser support for grid component, CSS custom properties

Better cross-browser support, ponyfill for css custom properties in IE, better icon default by removing fill from inline svg and setting fill in CSS, got around bug in IE11 flexbox child display when they have padding #59

Dropdown toggle button duplication fix and faux sidebar layout for Nodes

Fix cd-dropdown.js for issue with duplicate toggle button as described #55

Extend layout rules to include node faux sidebar template override and styles #57

Better layout with second sidebar, grid and filters components, inline search variant

Introduce second sidebar, refactor layout rules and page template to accommodate #52

grid component #47 #53

filters component and expand button component #54

inline search variant for Drupal search and views expose forms #50

dependency update #51

and issues #45, #48, #49

More components and layout improvements, dependency updates

Hero, banner, simple table component

Class on <main> when sidebar is rendered for column margins

#46
#45
#44

User menu improvements

better string to username menu item, fix second level user menu items floating when titles are short

Readme and breakpoints

Update readme with links to sub theme repo
Add breakpoints.yml with media queries matching CD variables