Api

Intentionally-static API. Currently supported:

```
Tilda::log
Tilda::delay (works both before and after FreeRTOS has started)
Tilda::setLedColor 
Tilda::createButtonSubscription
Tilda::openApp
```

Please add to that class if you create functions that could be used in different places.

This is _not_ intended to reflect "good" OOP programming practise, it's an attempt to reduce complexity and barrier-to-entry for people trying to get their own stuff working on the badge. For internal stuff feel free to use references passed into the constructor or similar.

Please try to document all functions here: https://docs.google.com/document/d/1ZaCsUq5Qp0DeIWdqenu-6Szdc2tQtGVmorv7q_eQSbk/edit