update release notes for 2.1.0

[jmborr]

Description of work:

Check all that apply:

• added release notes (if not, provide an explanation in the work description)
• updated documentation
• Source added/refactored
• Added unit tests
• Added integration tests
• Verified that tests requiring the /SNS and /HFIR filesystems pass without fail

References:

• Links to IBM EWM items:
• Links to related issues or pull requests:

Manual test for the reviewer

Check list for the reviewer

• release notes updated, or an explanation is provided as to why release notes are unnecessary
• best software practices
  • clearly named variables (better to be verbose in variable names)
  • code comments explaining the intent of code blocks
• All the tests are passing
• The documentation is up to date
• code comments added when explaining intent

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Please upload report for BASE (next@534137b). Learn more about missing BASE report.

Additional details and impacted files

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  Coverage        ?   82.36%           
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  Files           ?       20           
  Lines           ?     2280           
  Branches        ?        0           
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  Hits            ?     1878           
  Misses          ?      402           
  Partials        ?        0           

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