add relational quantity value #1875

[stap-m]

Summary of the discussion

A relational quantity value is a quantity value that quantifies two or more quantities in relation to each other.

• [x] > * Bezug von full load hours zu process über process atttribute performance
• [x] > * market share value zu fraction value
• [ ] > * ~area per power value als relational quantity value für specific space requirement~, will be done together with space requirement, see https://github.com/OpenEnergyPlatform/ontology/issues/1875#issuecomment-2301429924
• [x] > * annual GDP growth
• [x] > * discount rate
• [x] > * exchange rate
• [x] > * inflation rate
• [ ] > * ~all monetary prices,~ will be done in #1902
• [x] > * purchasing power parity

Type of change (CHANGELOG.md)

Add

• relational quantity value

Update

• fraction value, full load hours, market share value, annual gdp growth, discount rate, exchange rate, inflation rate, PPP

Remove

• Removed a broken link #

Workflow checklist

Automation

Closes #1911

PR-Assignee

• [ ] 🐙 Follow the Pull Request Workflow
• [ ] 📝 Update the CHANGELOG.md
• [ ] 📙 Add #'s to term tracker item

Reviewer

• [ ] 🐙 Follow the Reviewer Guide
• [ ] 🐙 Provided feedback and show sufficient appreciation for the work done