[ENH] Add major OS executables on new release

[SamGuay]

This PR adds a GH workflow that builds and adds executable files for the 3 main programs, namely dcm2bids, dcm2bids_helper, and dcm2bids_scaffold, when a new release is published.

This workflow will run only when there is a new release and will build executables for Windows, Linux and macOS. I have set the executable bit, so technically chmod u+x dcm2bids* won't be needed as well.

See https://github.com/SamGuay/Dcm2Bids/releases/tag/3.0.0-alpharc for an example.

Caveat: Windows and macOS builds haven't been tested. Linux bin works properly on Ubuntu 20.04 and up. Ideally, the build would be done on CentOS 7 but GH doesn't have CentOS runners... so the bins might need to be recompile to work on HPC running RHEL-based OSes.

[codecov-commenter]

Codecov Report

Merging #221 (684c925) into master (8ab482e) will increase coverage by 1.75%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #221      +/-   ##
==========================================
+ Coverage   78.05%   79.80%   +1.75%     
==========================================
  Files          15       15              
  Lines         925      931       +6     
  Branches      180      184       +4     
==========================================
+ Hits          722      743      +21     
+ Misses        167      150      -17     
- Partials       36       38       +2     

Flag	Coverage Δ
pytest	79.80% <ø> (+1.75%)	⬆️

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see 5 files with indirect coverage changes