feat(tools): add basic makefile, to prevent confusion on how to setup tests

[itsdevbear]

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 83.92%. Comparing base (e314ffd) to head (55e03c6). Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #21   +/-   ##
=======================================
  Coverage   83.92%   83.92%           
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  Files          61       61           
  Lines        3035     3035           
=======================================
  Hits         2547     2547           
  Misses        323      323           
  Partials      165      165           

Components	Coverage Δ
ssz	83.24% <ø> (ø)
sszgen	70.99% <ø> (ø)

[karalabe]

Wondering whether it would be better to just have a section about it in the readme. For example the tests repo relies on git LFS, which the user would need to install/enable separately. I'd guess that's not possible to outsmart with a Makefile, in which case we're only partially covering the issue.