Raise the version number to 2.1.0

Description

Increases the version number to celebrate the fixing of a bug (!128 (merged)), and the introduction of more features (!126 (merged)).

Changes

Changes the version number to 2.1.0.

Test and Review

To be filled in by the reviewers

• There are no unnecessary files present in the MR

• The continuous integration has no problems with the MR

• The MR is filled in as requested (including labels, milestones, and reviewers)

• The documentation is up-to-date

• !126 (merged) has been merged

• !128 (merged) has been merged