feat: FastEmbed embedding support (#291)

### Description

Following up on https://github.com/infiniflow/ragflow/pull/275, this PR
adds support for FastEmbed model configurations.

The options are not exhaustive. You can find the full list
[here](https://qdrant.github.io/fastembed/examples/Supported_Models/).

P.S. I ran into OOM issues when building the image.

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

---------

Co-authored-by: KevinHuSh <kevinhu.sh@gmail.com>

requirements.txt

@@ -27,6 +27,7 @@ elasticsearch==8.12.1
 elasticsearch-dsl==8.12.0
 et-xmlfile==1.1.0
 filelock==3.13.1
+fastembed==0.2.6
 FlagEmbedding==1.2.5
 Flask==3.0.2
 Flask-Cors==4.0.0