Add enhanced leader data

[FloTeu]

As a user i want to get some more information about the leader than just the id. Therefore, we need to save further information.

TODOs:

• [x] Decide which data source to use (firestore vs bigquery)
• [x] Decide data schema (required are for example name, colors, image (normal, alt art), life, power, attribute, ability, release_meta)
• [x] Update leader image data to data source (e.g. google cloud storage)
• [x] Implement Code to initially create information to new data source (maybe with crawler?)
• [x] Create a frontend admin page to add new leaders dynamically (Only admins should see the page)

AC:

• Leader information is included in a accessible data source

[FloTeu]

Nearly finished task with latest commits. Data can be found in BQ dataset "leaders" and table "leaders"