Feature `extend-diff-expander` does not work in compare view #3916

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1. Make sure the bug is caused by Refined GitHub

Yes

2. Full URL where the bug appears

• https://github.com/microsoft/TypeScript/compare/v4.1.2...v4.1.3
• https://github.com/ember-cli/ember-new-output/compare/v3.22.0...v3.23.0

3. Video of the bug

https://user-images.githubusercontent.com/47531779/106135680-2a568500-6160-11eb-810d-21b7a58f03df.mov