add support for zstd compressed maps

[obiot]

While zstd support is pretty easy to add, it kind of defeat the purpose of using compressed maps to save place as including a zstd javascript decompression library (such as https://github.com/OneIdentity/zstd-js) will increase the plugin size to more than 2.5MB.

So unless there is a massive request to add support for zstd, zlib and gzip are a way better option for a javascript project.