DOC: rename sphinx project name, dtoolkit -> my data toolkit

[Zeroto521]

• closes BLD: change pypi name from dtoolkit to my-data-toolkit #382
• whatsnew entry

[codecov]

Codecov Report

Merging #454 (d60233a) into main (b870cbd) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #454   +/-   ##
=======================================
  Coverage   99.50%   99.50%           
=======================================
  Files          24       24           
  Lines         608      608           
  Branches       81       81           
=======================================
  Hits          605      605           
  Misses          1        1           
  Partials        2        2           

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