fix: support completing emotes starting with `:` #10257

Job	Run time
Build Ubuntu in Docker (ubuntu-20.04, ghcr.io/chatterino/chatterino2-build-ubuntu-20.04:latest, 6...	10m 6s
Build macos-13, Qt 5.15.2 (LTO:false, crashpad:on)	8m 52s
Build Ubuntu in Docker (ubuntu-22.04, ghcr.io/chatterino/chatterino2-build-ubuntu-22.04:latest, 6...	9m 55s
Build Ubuntu in Docker (ubuntu-24.04, ghcr.io/chatterino/chatterino2-build-ubuntu-24.04:latest, 6...	12m 7s
Build windows-latest, Qt 6.7.1 (LTO:false, crashpad:on)	14m 46s
Build windows-latest, Qt 5.15.2 (LTO:false, crashpad:off)	12m 36s
create-release	0s
	1h 8m 22s

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