Add Code_of_Conduct, Contributions and WaveDiff_Dev_Workflow markdowns

[jeipollack]

I prepared three Google Docs which should be converted to Markdown files:

• CODE_OF_CONDUCT.md
• CONTRIBUTING.md
• DEV_WORKFLOW.md

Save the files in the top-level of the repo.

Update the documentation file: https://github.com/CosmoStat/wf-psf/blob/main/docs/source/index.rst?plain=1 by adding at the bottom:

Contributing
------------

For information on how to contribute to the development of WaveDiff, see
`Contributing to WaveDiff <./CONTRIBUTING.md>`_.

Make sure the links work.

[jeipollack]

Hi @nadamoukaddem I granted you edit access, but if there are changes you would like to propose please you suggest them instead of editing the document directly. Thanks

[nadamoukaddem]

Hi @jeipollack , should I include the last paragraph in DEV_WORKFLOW.md ?

[jeipollack]

Hi @jeipollack , should I include the last paragraph in DEV_WORKFLOW.md ?

Hi @nadamoukaddem, thanks for catching this. Omit it from the new markdown file.

[nadamoukaddem]

Hi @jeipollack , I added the files and updated the documentation file, but when I opened the pull request, I didn't pass the test with pytest. I'm also having the same issue when running the tests on #112.