When a developer attaches the "preview" label, a build is created
and published on https://preview.openttd.org/. After that, new
pushes to the PR are automatically build (as long as the "preview"
label exists).
If a non-developer attaches the "preview" label, it will be
removed.
Emscripten compiles to WASM, which can be loaded via
HTML / JavaScript. This allows you to play OpenTTD inside a
browser.
Co-authored-by: milek7 <me@milek7.pl>
Also, while at it, make it more like the upcoming release-workflow,
so they look a lot more similar.
Functional it should be the same, except that Windows should
now also output when a test fails.