Restructure Examples Gallery

[f-brinkmann]

We discussed the following

• We want to move the notebooks that introduce packages to the top to a new 'Getting started' section
  • pfar introduction
  • pyrato introductin
  • spherical harmonic based HRTF interpolation: rename to spharpy introduction and maybe change/update a little, update image
  • sofar and sofa: rename to sofar introduction, update image, maybe update
• The current 'Getting started' section could be renamed, e.g., 'In Depth' or 'Insights'
• The 'Applications Section' stays as is

@mberz, @sikersten, @hoyer-a fine for you?

[mberz]

Sounds good except for the spharpy one.
I think the notebook adds good value with the interpolation case. It's however not a good fit for a general introduction.
Probably a mix of the old existing notebooks is better suited as a general introduction. After updating of course. I'd suggest to keep the interpolation notebook as is (move to the application section) and use a new one for the introduction.