gource-captions.txt: Add David Moews' chordthm
gource-captions.txt: Add David Moews' chordthm

Add David Moews' contribution of chordthm.

This addition means that *everyone* who contributed
a Metamath 100 theorem is mentioned (by name) in the captions.
I think it'd be too busy to note every Metamath 100 contribution;
making sure everyone who contributed to the Metamath 100 has a named
mention seems like a reasonable altenative.

Signed-off-by: David A. Wheeler <9ae72d22d8b894b865a7a496af4fab6320e6abb2@dwheeler.com>

metamath/set.mm,metamath/set.mm,metamath/set.mm