Add unit support for percentages

Related to https://github.com/nomad-coe/nomad/issues/100. Starting from 0.21, Pint has built-in support for percentages. Unfortunately, also starting from that exact version, this Pint issue is preventing an easy migration as it breaks our parser code.

Tasks:

• Upgrade Pint, once multiplication issue is solved.
• Ensure that new unit definitions get migrated to the front-end.
• Update JS unit code to support percentages.
• Add tests for the JS unit code.

added feature label

assigned to @himanel1

created branch 1945-add-unit-support-for-percentages to address this issue

added current label

changed the description

changed the description

marked the checklist item Add tests for the JS unit code. as completed

marked the checklist item Update JS unit code to support percentages. as completed

marked the checklist item Ensure that new unit definitions get migrated to the front-end. as completed

added backlog label and removed current label

mentioned in merge request !2386 (closed)

mentioned in merge request !2387