Cocogitto as commit backend

# Describe the solution you'd like

It would be nice to commit using [cocogitto](https://github.com/cocogitto/cocogitto) from inside gitui so that working on repos following [conventionalcommits](conventionalcommits.org) would be:

1. typo-free: by checking whether the commit name follows the convention.
2. less typing: choosing the type and scope of a commit from menus.

# Possible implementation

An option asking for the **commit backend**: whether to use _git commit_ or _cog commit_ (with normal git as default _and maybe if the repository has a cog.toml, cog as default?_)
when the option is enabled, show a prompt menu during commit.

Prompt can look something like this:

| Prompt | Description |
| ------------------ | ---------------------------------------------------------------------------------------------- |
| **type** | (_scrollable?_) menu of all types of commits that cocogitto recognizes¹ under this repository. |
| **body+footer** | the normal gitui commit message prompt |
| **optional scope** | menu of all scopes cocogitto recognizes¹ |
| **optional flags** | list of bool flags shown as buttons. For example: _breacking change?_ |

¹: I mean which are either in the default list of cocogitto or declared inside cog.toml. Maybe cocogitto exposes enabled options?

# Additional context

- I want to know your opinions: what could be improved? What is missing?
- I'm no rust wizard but I could give it a go and try implementing this :)

Es werden keine Dateien, Tests oder Einstiegspunkte genannt. Beginne damit, den bestehenden Commit-Ablauf von gitui nachzuverfolgen und die von Cocogitto unterstützten Typen, Scopes, Flags und die cog.toml-Konfiguration zu prüfen. Als abgeschlossen gilt die Arbeit, wenn das Design vereinbart ist und die Option für das Commit-Backend, die conventional-commit-Eingabeaufforderungen und der normale Git-Standard mit Abdeckung für beide Backends implementiert sind.

Vom Indexierungsmodell aus dem Issue-Text verfasst.