docs(backport): Add dev instructions and fix typos

[matthewfeickert]

Description

Backport components of:

• PR feat: Add nox support #2046
• PR fix: Use non-gui matplotlib backend for tests to avoid hanging on ipywidgets interact #2098
• PR docs: Use 'develop' extra over removed 'complete' #2113
• PR docs: Use 'req@url' syntax to install from remote VCS #2115
• PR feat: Add Python 3.11 to testing and default to using it #2145
• PR docs: Correct 'tensorflow' typo in v0.7.1 release notes #2198

Checklist Before Requesting Reviewer

• Tests are passing
• "WIP" removed from the title of the pull request
• Selected an Assignee for the PR to be responsible for the log summary

Before Merging

For the PR Assignees:

• Summarize commit messages into a comprehensive review of the PR

* Backport components of:
   - PR https://github.com/scikit-hep/pyhf/pull/2046
   - PR https://github.com/scikit-hep/pyhf/pull/2098
   - PR https://github.com/scikit-hep/pyhf/pull/2113
   - PR https://github.com/scikit-hep/pyhf/pull/2115
   - PR https://github.com/scikit-hep/pyhf/pull/2145
   - PR https://github.com/scikit-hep/pyhf/pull/2198

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Codecov Report

❗ No coverage uploaded for pull request base (release/v0.7.x@aa683bf). Click here to learn what that means.
Patch has no changes to coverable lines.

Additional details and impacted files

@@                Coverage Diff                @@
##             release/v0.7.x    #2206   +/-   ##
=================================================
  Coverage                  ?   96.51%           
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  Files                     ?       69           
  Lines                     ?     4532           
  Branches                  ?      646           
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  Hits                      ?     4374           
  Misses                    ?      123           
  Partials                  ?       35           

Flag	Coverage Δ
unittests-3.10	96.31% <0.00%> (?)
unittests-3.7	96.29% <0.00%> (?)
unittests-3.9	96.35% <0.00%> (?)

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