feat(issue-41): set and inherit labels

fix https://github.com/kiegroup/git-backporting/issues/41

test/support/mock/github-data.ts

@@ -91,7 +91,15 @@ export const mergedPullRequestFixture = {
 
   ],
   "labels": [
-
+    {
+      "id": 4901021057,
+      "node_id": "LA_kwDOImgs2354988AAAABJB-lgQ",
+      "url": "https://api.github.com/repos/owner/reponame/labels/original-label",
+      "name": "original-label",
+      "color": "AB975B",
+      "default": false,
+      "description": ""
+    }
   ],
   "milestone": null,
   "draft": false,

test/support/mock/gitlab-data.ts

@@ -241,7 +241,7 @@ export const MERGED_SQUASHED_MR = {
   "source_project_id":76316,
   "target_project_id":76316,
   "labels":[
-     
+     "gitlab-original-label"
   ],
   "draft":false,
   "work_in_progress":false,