Using a Makefile instead of docker-compose.yml for doc-en

Hi, I've created a Makefile for the doc-en repository that runs docker directly for doing smoke-testing/building. It will use an adjacent doc-base and/or phd if it finds them, which was my original motivation. There's also a php target if you want to build the web version of the manual. https://github.com/php/doc-en/pull/3673 With this, instead of running docker-compose up to build, you'll just need to run make. (The README.md has been updated.) I'll push it next week unless there are objections here. There's also a pending PR for the phd repo that adds a Makefile for running the test suite there: https://github.com/php/phd/pull/147 Thanks. Jim