doc: create maintaining folder for deps

I would like to receive some feedback on this idea. I wanted to move all the maintaining-x files under a common folder and I have created an overview file that lists all the dependencies and in a second iteration their version that will be updated by the tools.yml action. Should we keep the name of the md files maintaing-x or just x? @nodejs/security-wg Refs: https://github.com/nodejs/security-wg/issues/828