fix: use appropriate readonly for Generable interface (#168)

TS interfaces do not actually support the `get`-syntax, and instead should define the property as `readonly` if there is only a getter expected. The usage of `get`/`set` is otherwise left as an implementation detail, not an type definition.

Author: vpanta

src/lib/Components/index.ts

@@ -18,5 +18,5 @@ export interface Generable {
   /**
    * Type of generable object
    */
-  get generableType(): GenerableType;
+  readonly generableType: GenerableType;
 }