Add comment for Spork.Version

Co-authored-by: Jordan Schalm <jordan.schalm@flowfoundation.org>

Author: tim-barry

config/config.go

@@ -112,7 +112,10 @@ type Spork struct {
 	Next        *Spork
 	Prev        *Spork
 	RootBlock   uint64
-	Version     int
+	// Version is a Rosetta-internal version number that tracks Rosetta compatibility with Flow network versions.
+	// This version number is incremented each time there is a Flow network upgrades which includes a breaking change for Rosetta.
+	// Not all Flow network upgrades cause breaking changes for Rosetta, so this version number is not incremented for every network upgrade.
+	Version int
 }
 
 func (s *Spork) String() string {