Conventional commit aid

**Is your feature request related to a problem? Please describe.**
I would like to easily perform conventional commits (ideally with gitmojis) using GitUI.

**Describe the solution you'd like**
I would like an option to enable something like the [VSCode Conventional Commits](https://marketplace.visualstudio.com/items?itemName=vivaxy.vscode-conventional-commits) plugin, that prompts the user for the scope, etc. and builds the commit message from that.

Some [custom command](https://gist.github.com/timhagel/28ae03354a85ce3e5237b308912b9b52) support could also be implemented but I understand that would be a lot harder and maybe even out of scope for the project.

**Describe alternatives you've considered**
I could type them by hand, but I'd probably mess up (and wouldn't remember all the gitmojis). I could also try to find a CLI tool to do it and commit outside of GitUI, but it would mess up the workflow. Maybe gitmoji support would be sufficient.

Es werden keine Dateien oder Tests genannt. Beginne damit, den bestehenden Commit-Workflow von GitUI zu überprüfen, und entscheide, ob der Umfang Prompts für conventional-commit, gitmoji-Unterstützung, benutzerdefinierte Befehle oder eine kleinere Teilmenge umfasst. Done sollte eine vereinbarte Interaktion, unterstützte Nachrichtenfelder sowie Tests oder eine dokumentierte Verifizierung für das ausgewählte Verhalten umfassen.

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