feat(statistics): display some stats in the logs (#337)

* test: add more coverage

* docs: reorder and enhance typo

* docs(contributing): add more information about the npm scripts

* feat(statistics): add simple statistics

* feat(statistics): add more stats

* refactor(issues-processor): remove some options from the constructor

it should have been only useful for the tests

* feat(statistics): add stats for new stale or undo stale issues

* chore(rebase): handle rebase conflicts

src/classes/issue.spec.ts

@@ -52,7 +52,8 @@ describe('Issue', (): void => {
       exemptPrAssignees: '',
       exemptAllAssignees: false,
       exemptAllIssueAssignees: undefined,
-      exemptAllPrAssignees: undefined
+      exemptAllPrAssignees: undefined,
+      enableStatistics: false
     };
     issueInterface = {
       title: 'dummy-title',