x/tools/present: parse presenter notes and record them in Section struct

This is the first of a series of changes that add support for
speaker notes to the Go present tool. This is done by displaying
slides with speaker notes on a second window, and synchronizing
both windows.

Updates golang/go#14654

Change-Id: Ic7b158d1e40f9e7e58d01791c88909f5619ce87f
Reviewed-on: https://go-review.googlesource.com/21485
Reviewed-by: Andrew Gerrand <adg@golang.org>
1 file changed