Caching

Problem/Motivation

Implement caching in the same/similar way the Path Alias module did.

Proposed resolution

Investigate caching in the context of the following files:
- core/modules/path_alias/src/EventSubscriber/PathAliasSubscriber.php
- core/modules/path_alias/src/AliasManager.php

Implement something like that for our module:
- src/EventSubscriber/SeoUrlSubscriber.php
- src/SeoUrlManager.php