Extract "Code Strategy Assessment Framework" into its own pattern

The Unified Source Code Inventory mentions the concept of a Source Code Strategy Assessment Framework.

I believe that such a framework could be useful even for companies that are only using a single version control system, and hence don't need to unify their source code inventory further (because they already have a single inventory).

Therefore I am proposing to pull the Source Code Strategy Assessment Framework into a pattern of its own, which can then be references from the Unified Source Code Inventory and other patterns.

patterns/1-initial/source-code-inventory.md から始め、trieshard/source-strategy-assessment にあるリンク先の Source Code Strategy Assessment Framework を確認してください。framework を独立した pattern として定義し、その後、Unified Source Code Inventory およびその他の関連する pattern を更新して、そこを参照するようにしてください。framework が独立してドキュメント化され、既存の参照がそこを指していれば完了です。