message: Implement comments at the Bril syntax level.
diff: @@ -174,6 +174,9 @@ class JSONTransformer(lark.Transformer):
  def parse_bril(txt):
  + # Strip comments (must be entire line) from Bril before parsing
  + lines = [l for l in txt.split("\n") if not l.strip().startswith("//")]
  + txt = "\n".join(lines)
  parser = lark.Lark(GRAMMAR)
  tree = parser.parse(txt)
  data = JSONTransformer().transform(tree)
  