high contrast color palette

[ntno]

we should add a built-in high contrast color palette
the colors should meet WCAG guidelines

• https://webaim.org/resources/contrastchecker/
• https://accessibleweb.com/color-contrast-checker/

tasks:

• test color palette
• add example page to docs
• add link to palette page

[cowellbunga]

Created five new palettes during the palette review for #120 and the image examples are posted here.
They have been added to documentation and navigation in my local branch.

• blueberry: cream background and navy blue hyperlinks
• lightyear: hint of green background and pigment indigo hyperlinks
• red drum: double colonial white background and red berry hyperlinks
• soundside: peach background and sherpa blue hyperlinks
• volans: beige background and millbrook hyperlinks