Support for distilbert and spacy transformer models for text-encondings

[meetsoni15]

Currently its supporting six models as per downloadmodel.go file

var supportedModelsFiles = map[string][]string{
	"bart":       {"pytorch_model.bin", "vocab.json", "merges.txt"},
	"pegasus":    {"pytorch_model.bin", "spiece.model"},
	"marian":     {"pytorch_model.bin", "vocab.json", "source.spm", "target.spm"},
	"bert":       {"pytorch_model.bin", "vocab.txt", "tokenizer_config.json"},
	"electra":    {"pytorch_model.bin", "vocab.txt", "tokenizer_config.json"},
	"flair":      {"pytorch_model.bin"},
}

when we are trying to use GPL/dbpedia-entity-msmarco-distilbert-gpl for text encoding got below error

{"level":"fatal","error":"failed to convert model: unsupported model type: \"distilbert\"","time":"2022-11-30T10:37:21+05:30"}