refactor(team-map): replaces 'ajv' with a hand-rolled validation

[sverweij]

Description

• replaces the validation of the team map in ajv with a simple hand-rolled one
• removes the 3rd party production dependency 'ajv'

Motivation and Context

Less dependencies = less worries. Ajv is b.t.w. a great & well maintained package, but for validating the tiny team maps it's overkill. It also makes virtual-code-owners' footprint smaller (ajv is ~120kb minified/ ~35kb compressed - compared to vco itself which has the numbers ~27kb/ ~9kb).

How Has This Been Tested?

• green ci
• additional non-regression integration tests (we have to test a bit more now, but also the error messages can be easier made to fit to our use case).

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• Documentation only change
• Refactor (non-breaking change which fixes an issue without changing functionality)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• 📖

  • My change doesn't require a documentation update, or ...
  • it does and I have updated it

• ⚖️

  • The contribution will be subject to The MIT license, and I'm OK with that.
  • The contribution is my own original work.
  • I am ok with the stuff in CONTRIBUTING.md.