v0.9.0

PromptingTools v0.9.0

Diff since v0.8.1

### Added

• Split Experimental.RAGTools.build_index into smaller functions to easier sharing with other packages (get_chunks, get_embeddings, get_metadata)
• Added support for Cohere-based RAG re-ranking strategy (and introduced associated COHERE_API_KEY global variable and ENV variable)

### Commits

Merged pull requests:

• Refactor RAGTools (#56) (@svilupp)