fix (re-)compression of images (maplibre#579)

Compression middleware turned out to be hard to use for image cases - it
simply looks at the content-encoding, and if not set, tries to compress
if accepted by the client.

Instead, now individual routes are configured with either that
middleware, or for tiles, I decompress and optionally recompress if
applicable.

Now encoding is tracked separately from the tile content, making it
cleaner too. Plus lots of tests for mbtiles & pmtiles.

Fixes maplibre#577

cleanup readme versions

add v0.6 branch to CI

bump from yanked dependencies

set to v0.6

fix CI tests to include all targets and docs (maplibre#483)

need different names in CI

Rename build steps

Add separate build job in CI (maplibre#438)

This PR adds a separate build job in CI and installs OpenSSL for Windows
runner. Closes maplibre#437

add release trigger for the CI job