consolidate tsconfigs

We're accumulating a lot of tsconfig.json files in each package now. Lets create a tsconfig.json at packages/tsconfig.json (or should it be /tsconfig.json? or /tsconfig.base.json? we should follow best practices/patterns) that extends from the appropriate config from https://github.com/tsconfig/bases. Then each package in packages/**/tsconfig.json should extend packages/tsconfig.json and add their minimal set of unique overrides to it (e.g. maybe include/exclude paths).