feat: add GraphQL support to PactV4

- Refactors the GraphQL common utilities into a single package
- Refactors the V4 HTTP package into multiple files (lint)

Author: mefellows

examples/v4/graphql/.gitignore

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+src/*.js
+src/*.d.ts

examples/v4/graphql/.mocharc.json

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+{
+  "bail": true,
+  "reporter": "spec",
+  "colors": true,
+  "timeout": 60000,
+  "exit": true,
+  "require": ["ts-node/register", "source-map-support/register"]
+}

examples/v4/graphql/README.md

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+# GraphQL + Pact
+
+Demonstrates how to do Pact testing against a GraphQL endpoint. This is a POC, demonstrating how PactJS could provide a simple helper function that wraps the GraphQL request into a basic Interaction suitable for Pact (after all, GraphQL is simply an interface over HTTP).
+
+Test it out here:
+
+```
+npm run test:consumer
+npm run test:provider
+```