Support for `bge-small-en-v1.5` embedding model

[josephrocca]

Based on the MTEB leaderboard: https://huggingface.co/spaces/mteb/leaderboard it seems quite strong given its size. It's about half the size of gte-base, with performance that nearly matches it. That said, benchmarks can of course be deceiving and I haven't tested them myself, so if you've tested the bge models and haven't been impressed, then please feel free to close this.