docs: Markup board specific parameters

[hamishwillee]

This updates the parameter reference markdown output script to allow notes to be added to each parameter that is board-specific. You can either specify a group by name and apply the note to all parameters in the group, or specify particular parameters.

In this version the note is added to all parameters in "Actuator Outputs" group.

The note looks like this.

This comes from a discussion with @sfuhrer

[sfuhrer]

The info field is rather a bit large. Adds a lot of space to the docs. I would make it more discrete (lake a label, not a full info box, if possible), and otherwise would actually only add the info to the PWM_TIMx params. It's more hidden that some boards have different output pins associated with specific timer groups. While it's easy to see that some boards have only e.g. MAIN.

[hamishwillee]

@sfuhrer Thanks. To address your concerns about layout turned the note into a heading badge like this (ignore where they are applied - that was just to test rendering)

[sfuhrer]

@sfuhrer Thanks. To address your concerns about layout turned the note into a heading badge like this (ignore where they are applied - that was just to test rendering)

Yes that looks great!