agenda+ New approach for lreq docs

After discussions with Fuqiao, i am proposing a way to create new lreq 
materials that point to r12a orthography notes where (a) no additional 
information is available in the lreq doc, and (b) where some information 
exists that's not in the r12a doc but there is more in the r12a doc.

See an example of what it would look like at 
https://w3c.github.io/sealreq/khmer/indexnew.html

This approach removes the need to copy stuff from the r12a document to 
the lreq document (which is very time consuming busy work), and also 
simplifies maintenance (edit once only).

Note also that i experimented with a Contributors subsection at the top 
of the intro.

thoughts?

ri