Add empty scraper for the dossiers of the Senate

This mainly sets up the getProviderArguments() implementation.
Get the metadata of the dossier
Start documenting S/Dossier scraper in readme
Get the FR keywords of the dossier
[fix] Scope of selector was too large

The CSS selector used to get the rows of the first table of the page was actually selecting all the table rows of the page. This was breaking the parsing of authors in some cases, since the row containing them was selected using `$rows->last()`.
[fix] Scraper crashed when no keyword was present
Extract the list of documents
Move document number extraction to a method
[refactor] Simplify parseDocumentLinks()
Get the history items of the dossier
[refactoring] Simplify method
[refactor] Extract more logic out of method

Remove even more logic from the `getHistory()` method. This uses a ‘hacky’ trick by using instance properties to keep track of temporary values but it allows to greatly simplify and modularize the retrieval of the data. It also helps to make the code more readable.
[refactor] Extract retrieval of extra row data

This extracts the logic to retrieve any ‘extra’ row data to a dedicated method, so that adding logic to retrieve additional pieces of extra data would not clutter the main `getHistory()` method.
Add `textOfNode()` helper method on custom crawler
[refactor] Use `textOfNode()` helper method

This change makes the code more readable.
Get type of parliamentary procedure
Fix return type in docblock
Get the status data of the dossier
Make scraper able to work with multiple languages

The scraper now initializes a DOM crawler for each lang instead of a single one in French. This prepares it so that it will be able to extract data in multiple languages in upcoming revisions.
Get the NL title of the dossier