fix test workflow

[vezwork]

Following up on discussion in #770, lets try to get quarto extension tests working in the test github workflow.

Adds a build-vscode command to package.json and runs it in the workflow prior to tests in order to ensure that all necessary parts of the extension are built in the workflow prior to testing ✅🙂

• I have been amending the commit in this PR to play with the wait timing and the test can fail depending on the timing, which is a bit sketchy, but seems ok for now.

This was my first idea to try after #770 and it worked!

How the CI looks now

  Quarto basics
    ✔ Can open a Quarto document (178ms)
    ✔ Can edit in visual mode (2094ms)
    ✔ Roundtrip doesn't change hello.qmd (2335ms)
  3 passing (5s)

and heres a link to how it looked before (with two tests skipped in CI)

[juliasilge]

AMAZING 🤩

cc @lionel- I think this means you will be unblocked for writing a test for #755

[cscheid]

Wow, I believe you, but if we're cutting this short, then maybe we should bump it to a notably larger number?

I'm not sure that a 100/1600 ~ 6% increase is justifiable without a deeper understanding as to why the number would be consistently larger than 1600ms but consistently smaller than 1700.

[vezwork]

All I know is that I originally tried an additional await wait(APPROX_TIME_TO_OPEN_VISUAL_EDITOR after await extension().activate() and the tests passed in CI, then I removed that additional wait and the roundtripping test failed, then I adjusted this from 1600 to 1700 on the feeling that a bit of extra waiting seems to help and the tests all passed.

Altogether it is unclear what is happening. Extra waiting does seem to help. Its unclear where that waiting should be but it seems that the waiting does not have to be before switching to the visual editor.

[vezwork]

I expect this may take some finessing once we have seen more. I wouldn't be surprised if the tests flake on other PRs or once more tests are added or anything changes.

[cscheid]

I have a comment on those waiting numbers, but it's not important enough to hold off this extremely important PR!