Chapter for "hardening the system" or "maintaining the system"

[StephanStS]

Add items about

• Let's Encrypt: https://github.com/MichaIng/DietPi/wiki/Let's-Encrypt---Certbot
• TLS-SSL: https://github.com/MichaIng/DietPi/wiki/TLS-SSL
• Security recommendations: https://github.com/MichaIng/DietPi/wiki/Security-recommendation
• Fail2Ban: https://dietpi.com/phpbb/viewtopic.php?p=452#p452
• Backup/Restoring / Synching
• Updating
• Logfile viewing
• Disk space monitoring

[MichaIng]

Another addition, although not sure if this fits best into general security/hardening chapter or better into webserver/HTTPS section:

• Creating a self-signed TLS certificate, with proper SAN to allow encrypted and authenticated local network access via local IP(s) and/or hostname(s).
• Add a self-signed TLS certificate to the OS' Trusted Root Certification Authorities store.
• Related to Bitwarden docs, where this is required: https://dietpi.com/phpbb/viewtopic.php?p=28903#p28903

I'll add an example with the Bitwarden_RS docs port about how to do that on Windows 10. Would be great to add those for Android (multiple versions?), Linux and macOS as well, e.g. via content tabs. Once we decided or have a proper central chapter/section for this, we can copy the Bitwarden example and link it from wherever it might be relevant.

[nonnorm]

I could handle macOS, but because of my old computer my system is 2 versions out of date. Probably not much difference though.