Update changelog for version 0.9.1 #14

Job	Run time
Build and release (aarch64-unknown-linux-gnu, ubuntu-latest, gdscript-formatter-linux-aarch64)	2m 25s
Build and release (aarch64-apple-darwin, macos-latest, gdscript-formatter-macos-aarch64)	1m 29s
Build and release (x86_64-apple-darwin, macos-latest, gdscript-formatter-macos-x86_64)	1m 29s
Build and release (aarch64-pc-windows-msvc, windows-latest, gdscript-formatter-windows-aarch64.exe)	2m 30s
Build and release (x86_64-pc-windows-msvc, windows-latest, gdscript-formatter-windows-x86_64.exe)	2m 26s
Build and release (x86_64-unknown-linux-gnu, ubuntu-latest, gdscript-formatter-linux-x86_64)	1m 10s
	11m 29s

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