…iews

Increase author link visibility and link avatar
- `www/src/components/blog-post-preview-item.js`
- `www/src/templates/template-blog-post.js`

Ref #3199 #4354 #5396

Confirmed addition of
`transform: translateZ(0)`
in  blog-post-preview-item.js prevents image twitch in Chrome
when hovering the card, way to go @fk

...which glamor offers to increase specifity
(ref. https://github.com/threepointone/glamor/blob/master/docs/selectors.md)
via @fk review
`src/components/blog-post-preview-item.js`

Conflicts:
www/src/templates/template-blog-post.js
L 137
`fixed={post.frontmatter.author.avatar.childImageSharp.fixed}`

* upstream/master: (651 commits)
  chore(release): Publish
  [www] Gatsby/rebeccapurple banner (#6161)
  delay page transition until we have all resources (#6158)
  Fix old query results showing up in develop (#6159)
  Tidy up the remark example (#6160)
  fix displaying of graphql resolver errors (#6142)
  Move store assignment out of component. (#6150)
  [v2] Fix doc not centered (#6146)
  chore(release): Publish
  [gatsby-source-contentful] pass host to client init (#6149)
  [v2] migrate gatsby-plugin-feed to use new Link (#6147)
  Make getElementById Conditional (#6145)
  chore(release): Publish
  update yarn.lock
  Update plugins.md (#6099)
  add gatsby-starter-skeleton (#6141)
  [gatsby-source-mongodb] added support for extra connection string params (#5972)
  create public page renderer and export correct version (dev / prod) depending on NODE_ENV (#5986)
  Treat integers longer than 32 bit as floats. (#6082)
  Export graphql TypeScript definition from gatsby package (#6096)
  ...