Set up reusable workflows for stale PRs and formatting

[agnesgaroux]

Part of https://github.com/wellcomecollection/platform/issues/5740

We're moving away from using weco-bot for automated tasks in favour of github actions In order to make this easier to maintain, we want to:

• create reusable workflows in https://github.com/wellcomecollection/.github
• call them from the repos that needs them
• done here for - https://github.com/wellcomecollection/content-api

Repos currently using their own duplicated github workflow

• https://github.com/wellcomecollection/wellcomecollection.org
• https://github.com/wellcomecollection/storage-service
• https://github.com/wellcomecollection/catalogue-pipeline
• https://github.com/wellcomecollection/catalogue-api
• https://github.com/wellcomecollection/concepts-pipeline