Node 12 End-of-life on April 30th

Node 12 enters End-of-life on April 30, 2022 (https://endoflife.date/nodejs). From this date, new versions of Stencil CLI will drop support for Node 12, and add support for Node 14. In order to provide time for developers to update their Stencil development/deployment environments, we will not bump the required version of Stencil CLI to a version that requires Node 14+ until June 1, 2022.