* h_program-lang/ast_fuzzy.ml: comment
sgrep/spatch: documentation on ast_fuzzy.ml and the new way to match/transform

Summary:

Test Plan: visual

Reviewers: pieter, erling

CC: julienv, adonohue, ptarjan

Differential Revision: https://phabricator.fb.com/D805358

Blame Revision:

Task ID: