PR Summary example agent

A PR summary agent with GitHub integrations, automatically attaching a summary whenever a PR is opened/reopened. This PR also contains changes to the RAGTool and rag_helper: All the changes in #260, plus changing the document id to be created from `file path/file name` instead of `file name`, which prevents files with the same name in different folders from overriding each other. This occurs often with README.md files. Credit goes to @BrandonwLii for the RAG agent and GitHub integration, @BrandonwLii and @AbbyParo for the main agent, @efunchy for the git grep subagent, @jackmcau for the summary agent and grep `find_full_function` feature, and Michael Jonath for mentoring the team. [Video Demo](https://drive.google.com/file/d/1DoNLwypdec2B85TGTVcs_jbb2A2J-N0q/view?usp=sharing)