Add whats new page to documentation

[freemansw1]

Adds a "what's new" page to our documentation that auto-pulls from our changelog. Reformatted the changelog to have it look nicer on the site.

• Have you followed our guidelines in CONTRIBUTING.md?
• Have you self-reviewed your code and corrected any misspellings?
• Have you written documentation that is easy to understand?
• Have you written descriptive commit messages?
• Have you added NumPy docstrings for newly added functions?
• Have you formatted your code using black?
• If you have introduced a new functionality, have you added adequate unit tests?
• Have all tests passed in your local clone?
• If you have introduced a new functionality, have you added an example notebook?
• Have you kept your pull request small and limited so that it is easy to review?
• Have the newest changes from this branch been merged?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 64.70%. Comparing base (82ad04e) to head (b5d3777).

Additional details and impacted files

@@            Coverage Diff             @@
##           RC_v1.6.x     #545   +/-   ##
==========================================
  Coverage      64.70%   64.70%           
==========================================
  Files             27       27           
  Lines           3978     3978           
==========================================
  Hits            2574     2574           
  Misses          1404     1404           

Flag	Coverage Δ
unittests	64.70% <ø> (ø)

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[github-actions]

Linting results by Pylint:

Your code has been rated at 8.33/10 (previous run: 8.36/10, -0.03)
_{The linting score is an indicator that reflects how well your code version follows Pylint’s coding standards and quality metrics with respect to the RC_v1.6.x branch.
A decrease usually indicates your new code does not fully meet style guidelines or has potential errors.}