v1.8.0

React-Leaflet now has a website! Check out react-leaflet.js.org to browse the documentation.
If you wish to help out improving the website, this issue is a good starting point!

• Updated documentation and dependency to
  Leaflet v1.3.
• Add HTMLImageElement support to ImageOverlay (new in Leaflet v1.3).
• [website] Setup the website.
• [website] Fix links to examples (PR #430 by subelsky).