Unify the header text in instructions index page across the different microscope versions

In their index pages, all the microscope versions talk about the research papers, and have a section about finding the BOM and a statement that assembly is following a sequence of steps. After !342 (merged) there is also an information box about help on the Forum and issues in Gitlab.

Everything apart from the research papers is identical, but has to be maintained separately. To avoid maintaining multiple pages @julianstirling suggests an {{include:}} from a common file (!342 (merged) discussion)