Consider moving isaqb-logo.jpg to html-theme

[aheusingfeld]

I stumbled upon an inconsistency with the ISAQB logo.

1. we seem to have it in 3 places
   1.1. https://github.com/isaqb-org/advanced-template/blob/main/docs/isaqb-logo.jpg
   1.2. https://github.com/isaqb-org/advanced-template/blob/main/docs/images/isaqb-logo.jpg
   1.3 within the pdf-theme submodule
   Due to :imagesdir: images in setup.adoc, the first one is actually not in use.

2. As the pdf-theme contains its own version of isaqb-logo-without-text.jpg and isaqb-logo.jpg, wouldn't it make sense to do the same for html-theme?

3. Bonus question: Did we try to switch the logo format to PNG?

[programming-wolf]

1. Removed the first one in Remove redundant images #122
2. html-theme currently does not use any logo, but it should for each curriculum (as pdf-theme does).
3. No, why? I reduced the image size of the jpg a bit in Remove redundant images #122