Hook up MongoDB connection

[CephalonScientia]

Eventually, we would not solely depend on MediaWiki's Action API to fetch article content from wikis. There are three main reasons for doing so:

• So the app does not get blocked because of too many API requests
• Performance benefits for storing data on the edge
• To create a historical archive of article content

To achieve this, a database connection needs to be established to store cached versions of article content to be sent to the client. MongoDB is the preferred NoSQL database system to store document data like API calls that return a JSON response. For security reasons, the database connection string and other secrets should be stored in an environment file that will be ignored by Git.

[CephalonScientia]

To be done alongside issue #10