Add tests on reference version of no-namespace Ray Charles with ZSTD compression

[Jaifroid]

This issue supersedes #651. As soon as we have a reference no-namespace version of Ray Charles, we should beging to add tests that are specific to both a no-ns version and to ZSTD compression.

[kelson42]

@Jaifroid This will take a bit, because we need first to (1) release libzim7 (2) Update + release node-libzim (3) Adapt + Release MWoffliner (4) Publish a new ZIM file. All of this might take around 3 months.

[Jaifroid]

No problem, it's good to have the support in the app even if it takes some time for real-world ZIMs to be published. I just feel it's safer to write tests on a published ZIM, but if we get time, there's no reason we couldn't start on certain tests using the latest Ray Charles created by mgautier.