feat: description annotation

[lars-reimann]

Closes #517.

Screenshots (if necessary)

Testing Instructions

Select the element where you want to add the description annotation and add @description through the "Annotations" dropdown menu. Write a description and click "Save" to add the new description.
Description annotations can be also be found with the filter annotation:@description.

[github-actions]

MegaLinter status: ✅ SUCCESS

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✅ CREDENTIALS	secretlint	yes		no	3.74s
✅ GIT	git_diff	yes		no	0.01s
✅ KOTLIN	ktlint	6	0	0	16.49s
✅ TSX	eslint	12	0	0	11.35s
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[lars-reimann]

@Masara You only need to add changes to api-editor/gui. I already updated api-editor/backend and we don't keep api-editor/desktop in sync for now. The same applies to #537. I'll add a task list to the PR description with steps to complete.

[Masara]

Summary of Changes

In src/features/annotations/annotationSlice.ts:

• Add interface for DescriptionAnnotation
• Update AnnotationStore
• Update initialState
• Add upsertDescriptionAnnotation/removeDescriptionAnnotation reducers to annotationsSlice
• Export these two reducers
• Add and export selectDescriptionAnnotation selector

In src/features/ui/uiSlice.ts:

• Add interface for DescriptionUserAction
• Update UserAction

Other:

• Update src/features/annotations/AnnotationDropdown.tsx (sort entries alphabetically)
• Update all places that use the AnnotationDropdown
• Update src/features/annotations/AnnotationImportDialog.tsx; might replace the object in line 25 with the initialState from src/features/annotations/annotationSlice.ts, so we don't need to update this in the future
• Update src/features/annotations/AnnotationView.tsx
• Add form in src/features/annotations/forms
• Update src/app/App.tsx to show form when corresponding user action is active
• Add filter annotation:@description (src/features/packageData/model/filters/filterFactory.ts and src/features/packageData/model/filters/AnnotationFilter.ts)
• Update filter help text (src/common/FilterHelpButton.tsx)
• Update src/features/annotatedPackageData/model/InferableAnnotation.ts
• Update computation of number of annotations per element throughout the program (currently only heat map tags, later also Statistics View - Annotations #534)