Radarchart maxValue

In my use case I'm using a radarchart feeding real time data coming from a sensor to it, but the radarchart rescales depending on the values provided, making it difficult to understand.

It would be nice to have a parameter similar to maxX for linechart to prevent the chart to rescale.

If needed, my code is [here](https://gitlab.com/morecognition/remorder).

Start by locating the radar chart configuration and the existing line chart maxX implementation, then compare how their ranges are determined. Done means the radar chart accepts a fixed maximum value like the requested maxX parameter and no longer rescales when sensor data changes; add or update the relevant chart tests if the repository provides them.

Written by the indexing model from the issue text.