Documenting release 1.21; bumping version.
Merge branch 'master' of github-halostatue:halostatue/mime-types

* 'master' of github-halostatue:halostatue/mime-types:
  Add extensions appcache and manifest for text/cache-manifest
  Add extension webapp for application/x-web-app-manifest+json
  Add extension webp for image/webp
  Add extension svgz for image/svg+xml
  Add extension xpi for application/x-xpinstall
  Add extension crx for application/x-chrome-extension
  Add extension eot for application/vnd.ms-fontobject