add info about different hands in ms

[njr2128]

→ to be added after Marc confirms the exact hand characters (it is currently in PHS essay and the to be published in Marc’s)
Add to "about the manuscript" and "principles of transcriptions"

In particular, also add:
Hand D - Consistently, the hand adds this end of line horizontal strokes - what to say about them?
→ add to info about characteristic of hand D