Add issue template for abbreviations

[martijnvankekem]

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Important: make sure you create an issue first before submitting a pull request. Replace [ISSUE NUMBER] with the ID of the issue that is solved by this PR.

Closes #95

Proposed Changes

Explain the changes you've made with this PR

• Add an issue template for abbreviations at the top.

Checklist

• [x] I have read the contribution document.
• [x] I have added test cases to cover my changes (if applicable).
• [x] All new and existing test cases have passed.
• [x] My code adheres to the coding style of this project.