Use the ADR (Architectural Design Record) pattern for documenting significant decisions

[dbeatty10]

This is a:

• documentation update
• bug fix with no breaking changes
• new functionality
• a breaking change

All pull requests from community contributors should target the main branch (default).

Description & motivation

Quoting Michael Nygard:

One of the hardest things to track during the life of a project is the motivation behind certain decisions. A new person coming on to a project may be perplexed, baffled, delighted, or infuriated by some past decision.

Therefore:

We will keep a collection of records for "architecturally significant" decisions: those that affect the structure, non-functional characteristics, dependencies, interfaces, or construction techniques.

This PR seeds Nygard's original problem/solution strange loop into our project using the minimal amount of Markdown.

[jasnonaz]

This is fantastic, thank you for getting this set up @dbeatty10! ⭐