Add elm syntax regression test

[mdevlamynck]

Adds an elm example as part of the #1213 regression test suite. This is the triangle example from https://elm-lang.org/examples. The original file comes from https://github.com/elm/elm-lang.org/ where the license can be found.

[sharkdp]

The tests are failing. Could it be that you are not running the latest version of bat?

[mdevlamynck]

Indeed, my system was running an old version of bat. The highlighting is even better now ^^

I'm wondering, maybe the test script shouldn't rely on the system installed bat, but instead on a locally built version?

[sharkdp]

I'm wondering, maybe the test script shouldn't rely on the system installed bat, but instead on a locally built version?

I was wondering that too. We could run cargo run --release instead of bat, but that would potentially run a build first. It would also add a dependency on cargo (which is obviously a build depedency of bat, but isn't required for changes like this for now).

In the current version, the script gives control to the user on which version to use. We use this in our CI pipeline because there we want to run assets/create.sh first, then install bat, and then run the script, in order to test with the very latest syntax highlighting changes.