add TGS (telegram animated sticker) support

[agusibrahim]

hi, i added some stuff to support load gzip json data where is used in telegram animated sticker file (tgs). simply just load normally tgs file from asset or network

[xvrh]

@agusibrahim the next version (currently v3.0.0-alpha.1) will support loading .tgs file like this:

Lottie.asset(
  'sticker.tgs',
  decoder: LottieComposition.decodeGZip,
)

This is a bit different from your PR because:

• It uses the GZip decoder from package:archive. That way, it works on the web
• The decoder parameter trick allows for the GZip decoder to be tree-shaked if not used.

Let me know if it works for you.