Add glossary

According to a hint from #82 (closed), we should take the opportunity to make the abbreviation-filled texts a bit more readable by e.g. adding a mouse-over glossary.

• 👉 Review here (and all other pages)
• 👉 Edit dictionary

This adds something like this:

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Todo

• Added glossary stub
• Check practicability
• Add more abbreviations
• Streamline inconsequent writings, where obvious (HelmholtzAAI vs Helmholtz AAI ; IDP vs IdP) ....

Closes #82 (closed)