1.0.0-beta19

• Forked the Bootstrap 4 grid system for Shoelace
• Added custom media queries for xs, sm, md, lg, and xl breakpoints
• Added display utilities (e.g. hide-xs, hide-sm-down)
• Reduced switch sizes so they're not so gigantic compared to inputs
• Changed input-single to input-field since it's more semantic
• Added --label-color variable
• Added --input-addon-* variables
• Fixed :last-child margins so they only apply to direct descendents
• Added polyfill styles to force [hidden] elements to not display
• Documentation updates