add support for https://huggingface.co/BAAI/AltCLIP-m18

[xxaier]

add support for https://huggingface.co/BAAI/AltCLIP-m18

I created a pull request for export AltCLIP-m18 for onnx

https://github.com/FlagAI-Open/FlagAI/pull/322/files#diff-e0fa65fd7d57ecb0570cc6e05c2db4e3f26fcae4177f7eb7401dbc478b082077

Support for multilingual text search I think would be very useful

[infrawhispers]

Hey! That would be awesome - do you have a link to the raw ONNX file? assuming it follows existing CLIP models, we would just need to add an entry here.

I do have a mental todo to make adding custom models as simple as pointing to a config file.