docs: remove old symfony integration info and add new page with main Behat integrations

[carlos-granados]

Includes documentation about integrations with Mink, Symfony and Drupal.

In the end I did not add the mention of the integration with Laravel because the repository that has this extension (https://github.com/laracasts/Behat-Laravel-Extension) has not been updated for more than 6 years and does not work with more recent versions of Laravel. There is a more recent fork (https://github.com/soulcodex/laravel-behat) but seems much less popular. It looks like the Laravel community lost interest in Behat once Laravel Dusk was launched in 2017. I wonder if there may be a way to win them back 😄

Fixes https://github.com/Behat/docs/issues/165 and https://github.com/Behat/docs/issues/158

[carlos-granados]

@acoulton your input as a native English speaker is more than welcome 😄