Create sgd.dx
Create sgd.dx

Add an example optimizer, sgd with momentum, using generic vector space operations.

Co-Authored-By: dougalm <0bb64e81bea11b43bfc7c06c1607c3af64f31e6d@google.com>

google-research/dex-lang,google-research/dex-lang,google-research/dex-lang,google-research/dex-lang,google-research/dex-lang,google-research/dex-lang