- Supports a simple custom text setting for the help/support module in
the config
- Refactor the discord/"none" support settings to be more customizable
as well
- Add smart default for artifact store to simplify local development.
(By default artifacts will go into an ignored `./uploads` directory.)

When this is released we will need to change the prod `[support]` config
block to the following:

```
[support]
type = "text"
text = "For any other questions about PingPong usage, including enrollment issues, please contact <a class='underline' href='mailto:pingpong-help@hks.harvard.edu?subject=%5BPingPong%5D%20App%20support%20request'>pingpong-help@hks.harvard.edu</a>."
```