feat: Add exported version function

Pantograph.lean

@@ -2,6 +2,7 @@ import Pantograph.Goal
 import Pantograph.Protocol
 import Pantograph.Serial
 import Pantograph.Environment
+import Pantograph.Library
 import Lean.Data.HashMap
 
 namespace Pantograph

Pantograph/Library.lean

@@ -0,0 +1,8 @@
+import Pantograph.Version
+
+namespace Pantograph
+
+@[export pantograph_version]
+def pantograph_version: String := version
+
+end Pantograph