Add .htaccess for shared hosting https redirection

Static websites are easily deployed to shared hosting services but it lacks automatic redirection from http to https.

The can be solved with a `.htaccess` file in the `_site` folder:

```
AddDefaultCharset UTF-8
Options -Indexes +FollowSymlinks
RewriteEngine on
RewriteBase /
RewriteCond %{HTTPS} !=on
RewriteRule .* https://%{HTTP_HOST}%{REQUEST_URI} [R=301,L]
```