Add a scaffold of GraphQL architectural blueprint

doc/architecture/blueprints/graphql_api/index.md

+---
+stage: none
+group: unassigned
+comments: false
+description: 'GrahpQL API architecture foundation'
+---
+
+# GraphQL API
+
+[GraphQL](https://graphql.org/) is an open-source data query and manipulation
+language for APIs, and a runtime for fulfilling queries with existing data.
+
+At GitLab we want to adopt GrapQL to make it easier for the wider community to
+interact with GitLab in a reliable way, but to also advance our own engineering
+culture by modeling communicaton between backend and frontend components using
+GraphQL.
+
+This document describes the foundational work that is required to evolve our
+[GraphQL API](#link-to-graphql-docs) in a way that it is suitable for a
+large-scale production usage.
+
+## Summary
+
+## Challenges
+
+## Iterations
+
+## Status
+
+
+## Who
+
+Proposal:
+
+<!-- vale gitlab.Spelling = NO -->
+
+| Role                         | Who
+|------------------------------|-------------------------|
+| Author                       | Grzegorz Bizon          |
+| Architecture Evolution Coach | Kamil Trzciński         |
+| Engineering Leader           | Darva Satcher           |
+| Product Manager              | Patrick Deuley          |
+| Domain Expert                |                         |
+| Domain Expert                |                         |
+| Domain Expert                |                         |
+
+DRIs:
+
+| Role                         | Who
+|------------------------------|------------------------|
+| Product                      |                        |
+| Leadership                   |                        |
+| Engineering                  |                        |
+
+<!-- vale gitlab.Spelling = YES -->