Because:
* As we plan work for migrating the remaining content-server routes to
React, we need to nail down decisions regarding gql usage, where to
house the new routes, and how to plan for an incremental rollout
This commit:
* Adds an ADR summarizing the decision processes
Closes #https://mozilla-hub.atlassian.net/browse/FXA-6271
Co-authored-by: Lauren Zugai <lauren@zugai.com>
Mill