Check max uncompressed size in hex_tarball:unpack and unpack_docs

[wojtekmach]

Currently we only check the compressed max size.

See: https://github.com/hexpm/hexdocs/blob/97a7d2a8ecea503cd0e93e83e3e2417a8a6f67d3/lib/hexdocs/tar.ex#L14:L46