feat: add support for arrayContains matcher

[pepejeria]

📝 Summary of Changes

Adds support for the Pact v4 arrayContains matcher.

An arrayContains matcher checks that an array contains at least one element matching each of the provided variants, in any order (extra elements are allowed).

Changes:

• Sources/Matchers/ArrayContainsMatcher.swift (new):
  • ArrayContainsMatcher — serialises to the integration JSON the Pact FFI expects: { "pact:matcher:type": "arrayContains", "variants": [ … ] }.
  • ObjectMatcher — encodes a [String: AnyMatcher] variant as a plain JSON object (so nested matchers are extracted per-variant by the core).
• Sources/Matchers/Matcher+V4.swift:
  • Replaced the // TODO: "arrayContains" with two arrayContains(_:) overloads (object variants and general AnyMatcher variants).
• Tests/Matchers/MatcherArrayContainsTests.swift (new): serialisation tests (object variants, scalar variants, empty).

⚠️ Items of Note

• A dedicated struct is used rather than GenericMatcher because the JSON shape differs: arrayContains has a top-level variants array and no value field, whereas GenericMatcher always emits value and has no variants key.
• The emitted integration JSON was verified against the reference implementation (pact-foundation/pact-reference, pact_ffi/src/mock_server/bodies.rs).

🧐🗒 Reviewer Notes

💁 Example

try response.jsonBody(
    .like([
        "actions": .arrayContains([
            ["name": .equals("add-item"),    "method": .oneOf(["POST"])],
            ["name": .equals("delete-item"), "method": .oneOf(["DELETE"])],
        ])
    ])
)

🔨 How To Test

Run tests :)