Create a Flic Sampling Package

We should support the [Flic](https://flic.io/flic2) button. There is already a [Flutter plugin](https://pub.dev/packages/flic_button).

A `Measurement` could be:

```
FlicButtonMeasurement
timestamp
buttonId
event
click
doubleClick
hold
```

Note that the SDK supports listening for multiple buttons, which is good. But it requires some way to specify which buttons to listen to, and this can't really be hardcoded as button UUIDs. So need to somehow support a UI to pair with buttons.

Start by reviewing the existing Flutter flic_button plugin and the repository's sensing package conventions. Define the FlicButtonMeasurement fields and events, then determine how button pairing and selection should work for multiple buttons. Done means the package supports Flic button events and provides a way to choose which buttons to listen to.

Written by the indexing model from the issue text.