docker image fails to build

[nelimee]

As described in this comment, the docker image fails to build with the message

Step 8/20 : RUN crystal build ./src/invidious.cr     --static --warnings all --error-on-warnings     --link-flags "-lxml2 -llzma"
 ---> Running in 35591962efa4
Showing last frame. Use --error-trace for full trace.

In src/invidious.cr:26:1

 26 | require "compress/zip"
      ^
Error: can't find file 'compress/zip'

If you're trying to require a shard:
- Did you remember to run `shards install`?
- Did you make sure you're running the compiler in the same directory as your shard.yml?
ERROR: Service 'invidious' failed to build: The command '/bin/sh -c crystal build ./src/invidious.cr     --static --warnings all --error-on-warnings     --link-flags "-lxml2 -llzma"' returned a non-zero code: 1

Tested with commit 074497b.