Feature: Add a simple graph showing solar elevation in the terminal with the report subcommand

[mfreeborn]

It would be great if the report subcommand showed a simple line chart with time on the x axis and solar elevation on the y axis.

It would be even better if the chart could be annotated with, for example, sunrise, sunset and solar noon.

I've had a play around with textplots-rs, but it's missing a few key featrures:

• specifying y axis range
• specifying individual axis tick locations
• time-series axis labels
• annotations

Here is an example of what I can achieve with it up to its limitations:

And, for reference, this is the graph I would like to replicate:

[mfreeborn]

Plotters may be a better option, but the console backend is still WIP.

[nigels-com]

I was thinking of a similar visualisation, perhaps as SVG.
The broad idea is a progress-bar clock with annotations of sunrise, sunset and expected light level.
And the solstice plots for comparison.
The motivation is that we might have lost some situational awareness of what the sun is doing.