Link to documentation in samples

### Documentation Is:

- [X] Missing or needed?
- [ ] Confusing
- [ ] Not sure?

### Please Explain in Detail...

It would be useful if every sample had links to relevant documentation.

I'd be willing to contribute a first draft for every sample if you decide this is a good idea. Just need to know what the template would be before changing a bunch of files. [Put docs section at the top or at the bottom?]

### Your Proposal for Changes

I'd expect https://www.chartjs.org/docs/latest/samples/line/stepped.html to display something like

> ## Docs
> * [Line](https://www.chartjs.org/docs/latest/charts/line.html)
> * [Stepped](https://www.chartjs.org/docs/latest/charts/line.html#stepped)

And for https://www.chartjs.org/docs/latest/samples/scales/time-max-span.html :

> ## Docs
> * [Line](https://www.chartjs.org/docs/latest/charts/line.html)
> * [`spanGaps`](https://www.chartjs.org/docs/latest/charts/line.html#line-styling)
> * [Time Scale](https://www.chartjs.org/docs/latest/axes/cartesian/time.html)

### Example

_No response_