TODO before/after merging PR(https://github.com/Nitrokey/nitrokey-documentation/pull/272)

[Keksmo]

• find a solution to use toctrees for the features list on the index pages of the nitrokeys
• delete/edit some outdated articles, which are now duplicates of other articles (or duplicates of sections of other articles)
• fix translation
• test redirects (especially difference between the 2fa files for FIDO, U2F and TOTP because original files had very similar naming
• shorten some file names (i.e. openpgp files)
• replace product names with generic names (i.e. Nitrokey instead of Nitrokey FIDO2) in Feature pages when there is more than one product the article applies to