DOC: Add RocketPy change log file

[Gui-FernandesBR]

Pull request type

• ReadMe, Docs and GitHub updates

Checklist

• Tests for the changes have been added (if needed)
• Docs have been reviewed and added / updated
• Lint (black rocketpy/ tests/) has passed locally
• All tests (pytest --runslow) have passed locally

Current behavior

We often forget about what is being included in our releases.

New behavior

There's this CHANGELOG.md special file in the RocketPy root folder. This follows some internet standard format https://keepachangelog.com/en/1.1.0/

The idea is to update the changelog file every time we submit a PR that rings either a code addition, code change or code fix.
We must be short in the descriptions.

Breaking change

• Yes
• No

Additional information

Accepting suggestions before merging.
Thanks for bringing this out @giovaniceotto .

[giovaniceotto]

Great reference to https://keepachangelog.com/en/1.1.0/ @Gui-FernandesBR.

I have added a new checkbox to the PR template, leading users to update the new file.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (d7e4dba) 70.80% compared to head (a78d073) 70.80%.
Report is 9 commits behind head on develop.

❗ Current head a78d073 differs from pull request most recent head 5ba238c. Consider uploading reports for the commit 5ba238c to get more accurate results

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #472   +/-   ##
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  Coverage    70.80%   70.80%           
========================================
  Files           55       55           
  Lines         9234     9234           
========================================
  Hits          6538     6538           
  Misses        2696     2696           

Flag	Coverage Δ
unittests	70.80% <ø> (ø)

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[Gui-FernandesBR]

I almost forgot to include the link of this PR to the changelog.

All good now, thanks for the help @giovaniceotto !