Handle unknown and rm unused compressions

[nyurik]

• we only need gzip for now, so remove brotli and zstd
• add a new error case when dir compression is unsupported
• bump reqwest version dep
• add clippy warnings on unwrap and todo

[nyurik]

Note that zstd feature was just added in #38 and was never released, so can safely just drop it. CC: @RobWalt