Supply docs for barThickness

[jedrekdomanski]

Add docs for barThickness option in Bar chart

Fixes #5853

[benmccann]

It would be good to make this align with the docs for offsetGridLines. That means both that we should match the language (i.e. "This setting applies to the axis configuration.") and indentation (i.e. use 4-space indenting for the code sample)

[simonbrunel]

@jedrekdomanski I'm pretty sure that all options listed in the "Common Configuration" belong to the scale options, meaning that the following docs is wrong:

These options are merged with the global chart configuration options, Chart.defaults.global, to form the options passed to the chart.

@etimberg @benmccann can you confirm?

If so, instead of duplicating "This setting applies to the axis configuration", I would rename the parent section from "Common Configuration" to "Scale Configuration" and reword the introduction paragraph for something like:

## Configuration Options

The bar chart accepts the following configuration from the associated **scale options**:

// ... the options table ...

For example:

options = {
    scales: {
        xAxes: [{
            barPercentage: 0.5,
            barThickness: 6,
            minBarLength: 2,
            gridLines: {
                offsetGridLines: true
            }
        }]
    }
}

What do you think?

[jedrekdomanski]

If this is the case then yes, we should change that, although I am not an expert of Chart.js so I don't feel in a position to verify that. @etimberg @benmccann Can you confirm it?

[simonbrunel]

• barPercentage
• categoryPercentage
• barThickness
• maxBarThickness
• gridLines.offsetGridLines

[etimberg]

I believe these are all scale options, but I only skimmed the code

[simonbrunel]

@jedrekdomanski I think you can go ahead and fix the whole section instead.

[simonbrunel]

@jedrekdomanski should we also remove the similar part from offsetGridLines (line 167) since it's now redundant with the new doc?

This setting applies to the axis configuration. ... + snippet

[simonbrunel]

Thanks @jedrekdomanski