Add WFM example in docs

[nvaytet]

No description provided.

[YooSunYoung]

I just have a couple of minor comments but it seems nice : D

And one more question regarding the target audience.
If the target audience already know about WFM and just wants to know more about the WFM stitching methodology, I think it is fine as it is,
but if it is about introducing WFM stitching methodology, I think it'll be nice to add more diagrams or pictures to explain the concept instead of just showing the code. But that can be done in another time.

[YooSunYoung]

This part renders a bit funny.
Should it be rounded up?

[YooSunYoung]

I didn't get this sentence. Especially are a time part.

[nvaytet]

Because it should be "we use one of the openings in the WFM choppers at a time" ;-)

[nvaytet]

I just have a couple of minor comments but it seems nice : D

And one more question regarding the target audience. If the target audience already know about WFM and just wants to know more about the WFM stitching methodology, I think it is fine as it is, but if it is about introducing WFM stitching methodology, I think it'll be nice to add more diagrams or pictures to explain the concept instead of just showing the code. But that can be done in another time.

For the target audience, I wanted to link to the old notebook we have that introduces the technique. However, there are 2 things to consider.

1. I would like to move that notebook from that repo to a new one (probably scippneutron), so I felt like adding a link only to change it later was not great.
2. That notebook uses the old ess code to perform the WFM correction to tof, and I didn't want to confuse users who see one way of doing it there, and another one here...

[YooSunYoung]

Then we can add more link/general explanation later...!