Add a start date option to ignore old issues and PRs (#269)

* docs(readme): add a small precision about the operations-per-run

closes #230

* chore(lint): ignore the lib folder for prettier

* chore(date): add a function to check if a date is valid

* chore(date): add a function to get a humanized date

* chore(date): add a function to check if the date is more recent than

* feat(date): add a start date to ignore old issues and PRs

closes #174

* docs(readme): change the date to match the description

* chore(date): add a better type for the date

* docs(date): add missing JSDoc about the return type

* chore(rebase): fix issues due to rebase

* docs(readme): fix table formatting issues

src/enums/issue-type.ts

@@ -0,0 +1,4 @@
+export enum IssueType {
+  Issue = 'issue',
+  PullRequest = 'pr'
+}