Update release instructions with additonal commit steps

[kevin-bates]

In building the 0.7.0 release, there seemed to be some missing steps, primarily around the commit(s) of the (twice) updated _version.py file. It also includes the v prefix on the tag name (to be consistent with existing tags) - along with its push.

Another area I wasn't sure about was the authoring of the Release itself. I used the Generate release notes button to build the content, then added the contributors and full change log entries.

Also, I wasn't sure where the assets (assets_shas.json and metadata.json) come from, so not sure if their generation should be addressed in the instructions as well. Note that the 0.7.0 does NOT current include those assets.

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (f874ec6) 94.35% compared to head (59eaac4) 94.35%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #52   +/-   ##
=======================================
  Coverage   94.35%   94.35%           
=======================================
  Files          12       12           
  Lines         514      514           
=======================================
  Hits          485      485           
  Misses         29       29           

Impacted Files	Coverage Δ
pytest_jupyter/_version.py	100.00% <100.00%> (ø)

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[blink1073]

Thanks!