Update Image Capture pages

Image capture pages to be updated following feedback at Natsca training. Pages can be found [here](https://github.com/DiSSCo/dissco.github.io/tree/main/Digitisation/SpecimenImageCapture). They have been hidden from the navigation for now, although can still be found by going directly to the [URL ](https://dissco.github.io/Digitisation/SpecimenImageCapture/SpecimenImageCapture.html)

