feat: add diffpy.app runmacro <.dp-in file> entry point

[ycexiao]

What problem does this PR address?

Closes #6

Add an entry point and refactor the existing code.

diffpy.app runmacro <.dp-in>

What should the reviewer(s) do?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.46%. Comparing base (aad7c3d) to head (c0de591).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main       #7   +/-   ##
=======================================
  Coverage   92.46%   92.46%           
=======================================
  Files           4        4           
  Lines         146      146           
=======================================
  Hits          135      135           
  Misses         11       11           

Files with missing lines	Coverage Δ
tests/test_pdfadapter.py	100.00% <100.00%> (ø)
tests/test_runmacro.py	100.00% <100.00%> (ø)

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[ycexiao]

@sbillinge, it's ready for review.

[ycexiao]

All arguments are passed as list.

[sbillinge]

I merged this but I am a bit worried that we are not testing enough. It looked as if we were jut testing that the right variable values were parsed, but not testing anything about fucntionality or resulting code. Is that right?

[ycexiao]

Yes.

There are three layers: (1) the pdfadapter that wraps the diffpy.srfit (2) the textx that creates the parser grammar (3) the Parser that defines actions to take when specific command is read from the macro.

I think we don't need to worry too much about the first two layers, but the third layer needs more tests.