#51387 introduced a couple more top level files; .gulp.js and .git-blame-ignore-revs.

I really wish I could at least see the word "TypeScript" at the top of our readme when loading the pages, as silly as that sounds.

• .eslintignore can be moved into .eslintrc.json.
• .yarnrc could be removed (this file actually breaks the internal repo when checked out in-tree).
• CopyrightNotice.txt can be moved into scripts.
• Dockerfile and .dockerignore are for docker tests only, and could be moved into tests/cases/docker as Dockerfile and Dockerfile.dockerignore. Then, the docker test runner can set DOCKER_BUILDKIT=1 and use docker build -f ./test/cases/docker/Dockerfile with cwd set to the repo root to have things work.

I have a branch with each of these done, but I'm turning my TODO list into proper issues, so, filing.