message: Replace deprecated theme.maxWidths with theme.sizes
  In the styled-system v5.0.0 Changelog `theme.maxWidths` was replaced by `theme.sizes`
  This commit replaces the deprecated key so setting props like `maxWidth="medium"` works again.
diff: @@ -57,12 +57,6 @@ const colors = {
  const theme = {
  breakpoints: ['544px', '768px', '1012px', '1280px'],
  - maxWidths: {
  - small: '544px',
  - medium: '768px',
  - large: '1012px',
  - xlarge: '1280px'
  - },
  fonts: {
  normal: fontStack([
  '-apple-system',
  @@ -95,6 +89,12 @@ const theme = {
  formControl: 'rgba(27, 31, 35, 0.075) 0px 1px 2px inset',
  formControlFocus: 'rgba(3, 102, 214, 0.3) 0px 0px 0px 0.2em'
  },
  + sizes: {
  + small: '544px',
  + medium: '768px',
  + large: '1012px',
  + xlarge: '1280px'
  + },
  space: ['0', '4px', '8px', '16px', '24px', '32px', '40px', '48px', '64px', '80px', '96px', '112px', '128px']
  }
  