Update packer-plugin-sdk to use version 0.1 (#50)

A recent update in the packer-plugin-sdk was a breaking change in Packer's internal marshalling for communicating with plugins : hashicorp/packer-plugin-sdk#31

It could be that this project is not impacted, but updating to v0.1 will make sure it's not the case.
I didn't update the `go.sum` file, this will happen automatically next time you run `go ...` in the project folder.

go.mod

@@ -4,6 +4,6 @@ go 1.15
 
 require (
 	github.com/hashicorp/hcl/v2 v2.8.0
-	github.com/hashicorp/packer-plugin-sdk v0.0.11
+	github.com/hashicorp/packer-plugin-sdk v0.1.0
 	github.com/zclconf/go-cty v1.7.0
 )