ci: validate wit definitions

[ricochet]

This validates the wit definitions for both 0.2.* and 0.3.*

I have not added the update and publish workflows but will add those in a following PR once we land on the approach (use matrix for filter paths so we're only building what changed).

[yoshuawuyts]

After we merge this we should add the following ruleset to the repo via Settings → Rules → Rulesets → New ruleset → Import a ruleset so we require all status checks to pass before a PR can be merged:

{
  "name": "Require All Status Checks to Pass",
  "target": "branch",
  "enforcement": "active",
  "conditions": {
    "ref_name": {
      "include": [
        "~DEFAULT_BRANCH"
      ],
      "exclude": []
    }
  },
  "rules": [
    {
      "type": "required_status_checks",
      "parameters": {
        "strict_required_status_checks_policy": true,
        "do_not_enforce_on_create": false,
        "required_status_checks": [
          "Validate WIT"
        ]
      }
    }
  ],
  "bypass_actors": []
}

[yoshuawuyts]

Neatttt, ty!

[yoshuawuyts]

We went over this PR together earlier today; excited to be moving forward with this!