Update the "Get Started" example of the ph.x code

[mbercx]

No description provided.

[scilover]

builder.kpoints = q_points

[mbercx]

@mkotiuga you want to give this a quick read to see if it is clear? 🙃

https://aiida-quantumespresso--829.org.readthedocs.build/en/829/user_guide/get_started/examples/ph_tutorial.html#parameters

[sphuber]

@mbercx @mkotiuga would be good to merge this soon so we can release it with 4.0.1

[mkotiuga]

@mbercx @sphuber it looks OK to me as a very basic example.

If I'm being picky, there is some wording I would change/details I would clarify. If I were to add one thing, it would be a little more about the q-points - specifically that a 1x1x1 grid gives the gamma point (just to be very clear) and how you can specify a list of explicit q-points.

At some point it would be good to add the q2r and matdyn steps for calculating a dispersion...

[sphuber]

Thanks to both!