Use `Makefile` to improve developer experience

[anatoly-scherbakov]

#182 proposes to use a Makefile to automate the project. This issue provides reasoning for introducing that tool.

Why is that important?

An open source library has software developers as its target audience:

• as users,
• and as contributors.

To attract contributors, it likely benefits to improve their developer experience -- to ensure they enjoy the process of contributing to the project.

One of aspects of that could be saving them from tedious repetitive tasks, and Make can do that.

Updating submodules versions

git submodule update --remote --init --recursive

is rather lengthy and tedious to copy-paste from README.md all the time, -- and thus provides a better developer experience.

Running tests

We could do

make test

instead of, say, python tests/runtests.py.

CI

Such commands as make test can also be reused in GitHub Actions CI (assuming we do want to use those), thus reducing the repetition in the overall project repo.