docs(changelog): add v2.1.1 entries

[Serpentiel]

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About this change—what it does?

adds v2.1.1 entries to the changelog

What type of change is it?

• Documentation update, i.e. documentation-only change

• This change requires a documentation update

Have you checked yourself twice?

• Any dependent changes have been merged and published in downstream modules
• I have added tests that prove my fix is effective or that my feature works
• I have checked my code and corrected any misspellings
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have performed a self-review of my own code
• My changes generate no new warnings
• My code follows the contributing guidelines of this project