style: use CODE-OF-CONDUCT.rst, tests.txt and docs

[ycexiao]

What problem does this PR address

Closes #141.

use CODE-OF-CONDUCT.rst, tests.txt, and docs names.

[sbillinge]

This looks good. Is there a reason it is showing as being a draft?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.97%. Comparing base (edc5bd0) to head (d6541e9).
⚠️ Report is 2 commits behind head on migration.

Additional details and impacted files

@@            Coverage Diff             @@
##           migration     #142   +/-   ##
==========================================
  Coverage      98.97%   98.97%           
==========================================
  Files              6        6           
  Lines           1267     1267           
==========================================
  Hits            1254     1254           
  Misses            13       13           

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[ycexiao]

This looks good. Is there a reason it is showing as being a draft?

Sorry, it's ready for review now.

[sbillinge]

@ycexiao PDFfit2 was skpkged quite a long time ago. Could you do me a favor and try a package update on it and see if there are any other updates that are needed?

[ycexiao]

@sbillinge
Run

package update
cd diffpy.pdffit2
cp -r ../.git ./
git status

There are no files added by package update. Information added in the modifications is mostly comments in the CI files. The other modifications are not we want for this package.

I think there are not many updates needed in this package.

[sbillinge]

Sounds good. Make any changes you think. Bring the comments (why not) and anything else