Support <front> as a route

Thank you for your module, this is a solid addition to the Block ecosystem.

Problem/Motivation

Was expecting to be able to use the route <front>when setting the block visibility.

Steps to reproduce

Try to use <front> on a block route condition, and see that block does not appear. Only the actual route name of the current front page works. If the front page route changes, it breaks the original intention of showing the block on the "front" page.

Proposed resolution

Add the necessary code to detect if the current route matches <front> in \Drupal\route_condition\Plugin\Condition\RouteCondition::evaluate

Remaining tasks

User interface changes

API changes

Data model changes