"src/assets/add:removeChild.png" not an allowed filename on Windows

The colon is not allowed as part of a filename in Windows-Environments, making it impossible to checkout the repos head.

```
error: invalid path 'src/assets/add:removeChild.png'
fatal: unable to checkout working tree
warning: Clone succeeded, but checkout failed.
```

Current workaround is to download the code as Zip.