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/interfaces/issues-processor-options.ts

@@ -42,4 +42,5 @@ export interface IIssuesProcessorOptions {
   exemptAllAssignees: boolean;
   exemptAllIssueAssignees: boolean | undefined;
   exemptAllPrAssignees: boolean | undefined;
+  enableStatistics: boolean;
 }