add default value to workflow inputs

Author: vomba

.github/workflows/buid-vm-image-manual.yml

@@ -9,10 +9,12 @@ on:
         description: k8s version
         required: true
         type: string
+        default: "1.33"
       tag:
         description: ck8s capi version
         required: true
         type: string
+        default: "0.8"
 
 env:
   version: ${{ inputs.version }}-*