Add "procedure document explainer section" to README

[balotofi]

Go through the procedure documents and add a section to the readme referencing the document and explaining which member of the satellite team may need it, include a brief summary of what the document contains, and any extra thing the user may need to note

You may reference other documents in other repositories within this organisation, e.g for the assembly procedure, you may wan to reference where to find the CAD files to produce the structure first etc.