Add minmax annotation to plots

[lekroll]

cf. https://plotly.com/javascript/text-and-annotations/ for plotly implementation

Pseudocode

1. Store x range.
2. sort data by y value.
3. Get first item as first annotation point
4. Get last item as second annotation point
5. If x diff of 2 items < 1/4 x range, show only max. Else show both

[lekroll]

Only for timeseries