added deployment system definition

systems/deployment-system.md

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+# Deployment system
+
+## Stocks
+
+* Pull requests
+* Ready commits
+* Deployed commits
+* Incidents
+* Reverted commits
+
+## Flows
+
+* Code review rate
+* Deploy rate
+* Defect rate
+* Recovery rate
+* Debug rate
+
+## System
+
+* ___Pull requests___ are converted into ___ready commits___ based on ___code review rate___.
+* ___Ready commits___ convert into ___deployed commits___ at ___deploy rate___.
+* ___Deployed commits___ convert into ___incidents___ at ___defect rate___.
+* ___Incidents___ are remediated into ___reverted commits___ at ___recovery rate___.
+* ___Reverted commits___ are debugged into new ___pull requests___ at ___debug rate___.