Add custom flags to config

[SleeplessByte]

Supports exercism/javascript-test-runner#79.

This adds hand-written flags to the .meta/config.json files to be consumed by our tooling.

"version.tests.compatibility": "jest-27"

This doesn't do anything by itself, but jest 27 is technically a breaking change. Adding this to our config files allows us to:

• separate exercises that have been updated vs. those that are on pre-27 versions
• give special error messages if something timeout related happens. Why? Jest 27 imposes a standard 5s timeout on each individual test.
• track unupdated exercises the next time jest is breaking

"flag.tests.task-per-describe": true

This should generally be true for all concept exercises and false for all practice exercises. When true, the test-runner can calculate the task_id based on the describe in the test files. This PR also contains updates to the spec files to match this newly imposed format.

"flag.tests.may-run-long": false

When we see students complain about timeouts on naive implementations, we should turn this to true. Doesn't do something right now, but if we see it a lot, we can use it to actually impose a shorter timeout (in the runner) and then show guided help.

"flag.tests.includes-optional": false

When true, skipped tests with test.skip are present and optional. This allows us to:

• enforce in the test-runner that there are only skipped tests if this is true
• add a message in the analyzer that there are optional tests that the student can run via the CLI. We can add an informational message with data how to do that, even if they did run this via the CLI.

[junedev]

Skimmed this. LGTM

[junedev]

Would be good to add the things you explained in the description here in the test runner readme if you didn't do that already.

[SleeplessByte]

Yeah, I want to add it there, and also in our CONTRIBUTING guide, right?

[junedev]

🤷‍♀️ I don't have an overview yet what documentation should go where ... getting a better grip around the docs is still on my todo list. So I'm fine as long as you add it somewhere.

[SleeplessByte]

I am kinda leaning towards adding everything to the exercism.org/ javascript docs.