feat: add hybrid search for retrieval (#7)

Adds hybrid search capability to the rag. Default retrieval ist hybrid mode.

fix: Fix typos in question_rephrasing_prompt.py (#4)

Fix two typos in the question rephrasing prompt.

chore: remove Azure build and test pipeline (#2)

- remove Azure build and test configuration file. 
- adjust PR template
- adjust make file, gitignore
- add github action for linting and testing