Add empty scraper for the dossiers of the Chamber

This mainly sets up the getProviderArguments() implementation.
[composer] Require patchwork/utf8

Patchwork UTF-8 for PHP
https://github.com/nicolas-grekas/Patchwork-UTF8

Extensive, portable and performant handling of UTF-8 and grapheme clusters for PHP.

This is a dependency of `illuminate/support` but the package wrongly references it as a dev dependency instead of a normal one. Explicitly listing it in the main composer.json fixes the issue.
Add previousOne() and nextOne() to custom crawler

These are efficient and readable shortcuts to get the same results than `$crawler->previousAll()->first()` and `$crawler->nextAll()->first()`.
[doc] Fix return value in docblocks

Also fix a missing space between two words.
Add magic `__toString()` method to custom crawler
DRY the custom crawler a bit by extracting a throw