This is more or less straightforward migration of Buck codemirror
packaging rules: "jar" with non-minified JS version and "jar_r"
with minified JS version.
TEST PLAN:
bazel build //lib/codemirror:codemirror
bazel build //lib/codemirror:codemirror_r
Change-Id: I68a22902b5a24af9aa9479d27e6d160978631108