Offline Mode

Add docker container that locally hosts cheat.sh server which uses a database of _pre-downloaded_ cheat sheets and does not use the web **at all**. The container should ideally not need to be rebuilt when a new cheat-sheet is added or an old one is edited.

### Suggested offline mode features:
- [ ] Docker container web server
- [ ] Configuration file pointing to local cheat sheet repos
- [ ] Edit configuration live
- [ ] ZERO external connections (100% local)
- [ ] Template cheat sheets for different concepts (CLI commands, API docs, algorithms, communication protocols...) - Might be good to add this to the main cheat.sh too

### Use Case
I have a network of machines I like to use to test out malware from [The Zoo](https://github.com/ytisf/theZoo). I always keep this network isolated from my other machines. I often find myself in need of cheat.sh and would like to have a local version running in my isolated environment.

Begin by reviewing the current cheat.sh server and Docker support, then map how local cheat-sheet repositories and configuration would be loaded. Define completion around a containerized web server that uses only pre-downloaded sheets, supports configuration edits without rebuilding, and makes zero external connections.

Written by the indexing model from the issue text.