test: install necessary deps for testing

[barinali]

Proposed Changes

This pull request aims to demonstrate tests passing with the updated changes from lezer-feel. So, this branch should not be merged!

Checklist

Ensure you provide everything we need to review your contribution:

• Contribution meets our definition of done
• Pull request establishes context
  • Link to related issue(s), i.e. Closes {LINK_TO_ISSUE} or Related to {LINK_TO_ISSUE}
  • Brief textual description of the changes
  • Screenshots or short videos showing UI/UX changes
  • Steps to try out, i.e. using the @bpmn-io/sr tool

[Copilot]

Pull request overview

This PR adjusts dependency resolution to run the test suite against a specific lezer-feel git ref (intended to validate compatibility with changes coming from lezer-feel).

Changes:

• Replace the published @bpmn-io/lezer-feel dependency with a git-based lezer-feel dependency.
• Add an overrides entry intended to force @bpmn-io/lezer-feel to match the git dependency.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.