mazel: make helpers for monorepos

bazel(-ish) for Makefiles = mazel

mazel is a simple bazel-inspired Makefile-based build system for monorepos.

The goal is to not create another build system, rather we provide simple helpers around GNU make, along with common (though not required) Makefile patterns.

mazel provides:

1. Ability to execute make targets in one or more subpaths.
2. Dependency graph to allow execution of targets in a logical order. Either parsed from the package manager (e.g. poetry's pyproject.toml or npm's package.json).

mazel test //libs/py/common          # Runs `make test` for the common library
mazel test                           # Runs tests for any packages under the current directory
mazel format //libs/py               # Code formats all code under libs/py
mazel run //tools/docker/base:image  # Builds the base docker image

See https://mazel.readthedocs.io/ for more info