Add zst compression type support

[agraul]

Uses github.com/klauspost/compress/zstd to handle the decompression since there is no zstandard support in Go's standard library.

Fixes #36

[nodeg]

I already built the binary (with static linking due to being on Tumbleweed and running it on SLE15 SP5) with

go build -tags netgo,osusergo

executing this new binary with the new SL Micro 6.0 repo, works fine and the packages get downloaded:

/etc/dom.yaml:

storage:
  type: file
  path: /srv/mirror

scc:
  username: xxxxxx
  password: xxxxx
  repo_names:
    # SLE Micro
    - SL-Micro-6.0-Pool
    - SUSE-Manager-Tools-For-SL-Micro-6.0
    - SUSE-Manager-Tools-Beta-For-SL-Micro-6.0
  archs: [x86_64]

minima-mirror-ci-bv:~ # cat /usr/local/bin/dom.sh
#! /bin/bash

/usr/bin/date >> /var/log/dom.log
echo '---------------------------------------------------------' >> /var/log/dom.log
(/usr/local/bin/utils/minima_dom sync -c /etc/dom.yaml 2>&1) >> /var/log/dom.log
echo >> /var/log/dom.log

dom.log:

2024/07/05 08:31:04 Processing repo: https://updates.suse.com/SUSE/Products/SL-Micro/6.0/x86_64/product/?XXXXXXXXXXXXX
2024/07/05 08:31:04 Downloading repomd.xml...
2024/07/05 08:31:04 Downloading repomd.xml.asc...
2024/07/05 08:31:04 Downloading repomd.xml.key...
2024/07/05 08:31:04 repodata/ceac29442faf83503837c33974be82a0efb80f65da606884a5dc583afa2afd39e98c4f702415b62fb641c96e842bc54fe9560a080ff4e1afd1f58ac79833f140-primary.xml.zst
2024/07/05 08:31:04 ...recycling
2024/07/05 08:31:04 repodata/11cc78626afb6e471b0b11ca6f65eac7ba41a86976c7260eefbc8d93a7f368613b1dc34324815459f9a64564003e1c85c2fac04ad6d726be20ff645f11675959-filelists.xml.zst
2024/07/05 08:31:04 ...recycling
2024/07/05 08:31:04 repodata/53cb9077e04d8ba6c628bbc8224b2c762b904a385a1169efa0b541737ef808621c6050144ad808c641fd135d668d4262ff9b6aaf0b370eef4bc8970b46eb555b-other.xml.zst
2024/07/05 08:31:04 ...recycling
2024/07/05 08:31:04 repodata/91cb3f3af07d95002d5b3367b9c969ec640a9876fa06d8ea100193117ba22867c8d6b2c04411ae17f9aebe191eb9a5ddee8a58ef7b5718c21e56fd73d5e0d179-license-SL-Micro.tar.zst
2024/07/05 08:31:04 ...recycling
2024/07/05 08:31:04 repodata/79d62f9c4cae97a69fbb9a9a148733dedd65c16f8e31dae6c796cca1fac7d2698487520646770982df6d931cd2faf4cb3f9df68bdfdf7605af036f920d707f10-susedata.zh_CN.xml.zst
2024/07/05 08:31:04 ...recycling
2024/07/05 08:31:04 Downloading 1123 packages...
2024/07/05 08:31:04 Downloading (1/1123) Mesa-23.3.4-7.3.x86_64.rpm...
2024/07/05 08:31:04 Downloading (2/1123) Mesa-dri-23.3.4-7.3.x86_64.rpm...
2024/07/05 08:31:05 Downloading (3/1123) Mesa-gallium-23.3.4-7.3.x86_64.rpm...
2024/07/05 08:31:05 Downloading (4/1123) Mesa-libEGL1-23.3.4-7.3.x86_64.rpm...
2024/07/05 08:31:05 Downloading (5/1123) Mesa-libGL1-23.3.4-7.3.x86_64.rpm...
2024/07/05 08:31:05 Downloading (6/1123) Mesa-libglapi0-23.3.4-7.3.x86_64.rpm...
2024/07/05 08:31:05 Downloading (7/1123) ModemManager-1.20.6-5.12.x86_64.rpm...
(...)