- introduce new on_property field for Extractor allowing to define the property to use for the label extraction

- use property (if provided) and allow label extraction via this approach
  - FIX https://github.com/mikepenz/release-changelog-builder-action/issues/208

src/configuration.ts

@@ -9,7 +9,7 @@ export interface Configuration {
   empty_template: string
   categories: Category[]
   ignore_labels: string[]
-  label_extractor: Transformer[]
+  label_extractor: Extractor[]
   transformers: Transformer[]
   tag_resolver: TagResolver
 }
@@ -24,6 +24,10 @@ export interface Transformer {
   target: string
 }
 
+export interface Extractor extends Transformer {
+  on_property: 'title' | 'author' | 'milestone' | 'body' | undefined
+}
+
 export interface TagResolver {
   method: string // semver, sort
 }