Enable turning off pdf-annot-show-annotation highlight

[icmor]

The function pdf-annot-show-annotation receives an optional parameter highlight-p to turn off highlighting displayed annotations. I believe it would be a nice feature to allow users to set this parameter so that the two functions that use it: pdf-annot-create-context-menu & pdf-annot-list-display-annotation-from-id can be used without showing additional highlights.

Personally, I highlight very sparingly and the extra highlighting is not very useful. Allowing users to also customize the extra highlight might improve usability (eg. if their annotation properties use the same highlight color as the extra highlight) but a simple boolean switch would be a nice addition.

Thank you very much for your continued work, pdf-tools is amazing!