refactor & integrate searchers from findpapers

[kashyapm94]

the following searchers are to be refactored & integrated in this repo

• [ ] acm searcher
• [ ] arxiv searcher
• [ ] biorxiv searcher
• [ ] cross ref searcher
• [ ] ieee searcher
• [ ] medrxiv searcher
• [ ] opencitations searcher
• [ ] pubmed searcher
• [ ] rxiv searcher
• [ ] scopus searcher

[kashyapm94]

related commit cc98f4bdd1acb9f2e9e1d03f85db5216e2ed11d7