rewrite URLs to remove .html ending and always hide "index.html"

.htaccess

<IfModule mod_rewrite.c>
  RewriteEngine On
  RewriteBase /

  RewriteCond %{HTTP_HOST} !^$
  RewriteCond %{HTTP_HOST} !^www\. [NC]
  RewriteCond %{HTTPS}s ^on(s)|
  RewriteRule ^ http%1://www.%{HTTP_HOST}%{REQUEST_URI} [R=301]

  RewriteCond %{THE_REQUEST} ^GET\ (.*)\.html\ HTTP
  RewriteRule (.*)\.html$ $1 [R=301]

  RewriteRule (.*)/index$ $1/ [R=301]

  RewriteCond %{REQUEST_FILENAME} !-d
  RewriteCond %{REQUEST_URI} /$
  RewriteRule (.*)/ $1 [R=301]

  RewriteCond %{REQUEST_FILENAME}.html -f
  RewriteCond %{REQUEST_URI} !/$
  RewriteRule (.*) $1\.html [L]
</IfModule>

Removes all ".html" suffixes from URLs and always applies "www" before hostnames without a leading "www" prefix.