Compressing JSON: Gzip vs. Zstd

1301878 - (zstd) Implement support for Zstandard (zstd) - https://bugzilla.mozilla.org/show_bug.cgi?id=1301878

912902 - Investigate zstd for JS source string compression - chromium - https://bugs.chromium.org/p/chromium/issues/detail?id=912902