Improve Skylark documentation (concepts.md), wrt mutability and Python compatibility
Improve Skylark documentation (concepts.md), wrt mutability and Python compatibility

--
MOS_MIGRATED_REVID=103634198

davidzchen/bazel-website,davidzchen/bazel-website,bazelbuild/bazel-website,davidzchen/bazel-website,bazelbuild/bazel-website,davidzchen/bazel-website,bazelbuild/bazel-website