docs(maintenance): add processes tab (#1747)

* docs(maintenance): update mkdocs to support tabs

* chore(ci): add parallel test npm script

* chore(ci): add jest command

* docs(maintenance): add testing page to navbar

* docs(maintenance): add contributing info

* chore: update roadmap

* chore: update release drafter workflow to allow for manual trigger

* fix formatting

* docs: maintainers handbook

* chore: link to new location

* fix links

* Update docs/maintainers.md

Co-authored-by: Alexander Schueren <[email protected]>

---------

Co-authored-by: Alexander Schueren <[email protected]>

Author: dreamorosi

Diff for: docs/upgrade.md

@@ -13,4 +13,4 @@ This release includes some breaking changes, please take some time to review thi
     This guide is a work in progress. We'll update it as we get closer to the 2.0 release. If you have any questions, or want to follow the progress, please join the discussion on the [GitHub issue](https://github.com/aws-powertools/powertools-lambda-typescript/issues/1714).
 
 | Area | Change | Code change required |
-| ---- | ------ | -------------------- |
+| ---- | ------ | -------------------- |