Lighthouse audit for next.gatsbyjs.org

[m-allanson]

Running a lighthouse audit on next.gatsbyjs.org reveals a few issues that could be fixed:

• Text is invisible while webfonts are loading
• Uses inefficient cache policy on static assets - most (all?) of these are required.
  • is google tag manager and google analytics required?
  • where does woopra come from?
  • a lot of the docsearch CSS gets overridden, is it possible to reduce the size of that dependency?
• Links do not have a discernible name
• Background and foreground colors do not have a sufficient contrast ratio. (copy in @fk before taking this on)
• Browser errors were logged to the console - this seems like a bug in Gatsby
• Document does not have a meta description

These could be fixed by updating the site here: https://github.com/gatsbyjs/gatsby/tree/master/www

[m-allanson]

Done!