Add minimal features to demonstrate best practices

Collect best practices in readme as used

# Work plan

- [x] A database table to track latest high five (XML configuration) (is there a best practice to use JSON database spec lol?)
- [x] Best practice: Ensure all database columns have id primary key, created_at, updated_at, and foreign keys as needed
- [x] A database table or some way to make a configuration setting for the "high five emoji"
- [x] A page that is only accessible by admins to show the latest high five
- [ ] It allows to change the high five emoji, or it links to the settings page for changing the high five emoji (only allow specific emojis from a dropdown don't let them type anything in :-))
- [ ] Best practice: This (and all) configuration change is logged using Moodle Logging Module for auditability.
- [ ] Has a visible widget that can be added a user's main page they see when they login
- [x] The widget uses some custom JS and CSS
- [x] The JS is compiled with AMD and that process is documented
- [ ] Release process is automated, or at least fully documented so that latest module versions can be released on the Moodle plugin store