[OTHER] .NET icon folder is inconsistent with naming convention

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### What would you like to share?

The [naming convention](https://github.com/devicons/devicon/wiki/Naming-Conventions) for icon folders (and icons) is to join all the words in the name, without any delimiters. The .NET (dot-net) folder though, is inconsistent with this convention.

This can be fixed by renaming the folder and icons to be `dotnet` in one word. To ensure that `dot-net` still shows up in searches, it can be added to the list of altnames.
https://github.com/devicons/devicon/tree/develop/icons/dot-net
#### Folder
#### Icons

### Additional information

_No response_

Beginne im Ordner icons/dot-net und vergleiche dessen Ordner- und Icon-Namen mit dem Wiki naming-conventions. Benenne den Ordner und die Icons in dotnet um und überprüfe anschließend, dass dot-net weiterhin über die altname-Liste des Projekts verfügbar ist und die aktualisierten Icon-Assets korrekt gefunden werden.

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