[MLIR][Transform] Docs: add SMT extension section and fix Tune header (llvm#161560)

Author: rolfmorel

mlir/docs/Dialects/Transform.md

@@ -415,10 +415,14 @@ ops rather than having the methods directly act on the payload IR.
 
 [include "Dialects/TransformOps.md"]
 
-## Tuning Extension Operaiton
+## Tune Extension Operations
 
 [include "Dialects/TuneExtensionOps.md"]
 
+## SMT Extension Operations
+
+[include "Dialects/SMTExtensionOps.md"]
+
 ## Affine Transform Operations
 
 [include "Dialects/AffineLoopTransformOps.md"]