Gacha: Banner Details Page

[GanyusLeftHorn]

Description

Currently, both the "Details" as well as "History" buttons on gacha banners display the gacha record. This PR adds a very simple banner details page, which is displayed when a user clicks on "Details".

Some things to note:

• The page template is generally based on the gacha records page merged with PR Update gacha_records.html #436. I also retained the template copyright in the footer.
• The page uses the same id -> name mappings generated for the gacha records page, as introduced by PR Utils for gacha history record subsystem #421.
• This PR adds some translation keys to the language files. I have inserted the same keys in all four currently existing language files, but the translations are all in English (I don't speak any of the other languages).
• The page is very minimalistic and currently only lists the characters available in the banner pool. Further details like rates, pity etc. could be added later.

Screenshot (standard banner):

Type of changes

• Bug fix
• New feature
• Enhancement
• Documentation

Checklist:

• My code follows the style guidelines of this project
• My pull request is unique and no other pull requests have been opened for these changes
• I have read the Contributing note and Code of conduct
• I am responsible for any copyright issues with my code if it occurs in the future.