feat: generated c++ code reading support

[SGSSGene]

Generated code also supports reading files.

TODO:

• [x] update README.rst
• [ ] Add more unittests for this
• [x] Show case in cwl-cpp-auto

[codecov[bot]]

Codecov Report

Merging #748 (e657b2b) into main (0c872c8) will increase coverage by 0.03%. Report is 1 commits behind head on main. The diff coverage is 90.62%.

:exclamation: Current head e657b2b differs from pull request most recent head 1f46588. Consider uploading reports for the commit 1f46588 to get more accurate results

@@            Coverage Diff             @@
##             main     #748      +/-   ##
==========================================
+ Coverage   83.60%   83.64%   +0.03%     
==========================================
  Files          22       22              
  Lines        4538     4567      +29     
  Branches     1226     1233       +7     
==========================================
+ Hits         3794     3820      +26     
- Misses        482      483       +1     
- Partials      262      264       +2     

Files	Coverage Δ
schema_salad/cpp_codegen.py	81.59% <90.62%> (+0.78%)	:arrow_up:

[SGSSGene]

The cwl-cpp-auto PR is a demonstration of the load function of CWL files.

[SGSSGene]

Will you also update the README ?

Stating that C++ generation also supports imports and a link to the example? will add it.