CLI can't process B/W videos

[philippmwirth]

CLI can't process B/W videos

Running the lightly-embed command on black and white videos leads to this error:

RuntimeError: output with shape [1, 64, 64] doesn't match the broadcast shape [3, 64, 64]

One solution would be to convert the B/W image to RGB similar to how it's done in the image loader: https://github.com/lightly-ai/lightly/blob/57ec16a13adf32fd74551079a3a0a5f4e969ae4f/lightly/data/_image_loaders.py#L12