integrate the llm and versioncontrol packages in the pullpal package
* Functionality to select a Github issue, and generate an LLM prompt
from it (PickIssue)
* Functionality to parse LLM response (from string or file), update
local git repository, and create pull request (ProcessResponse and
ProcessResponseFromFile)
Added "version control client" interface and created a Github
implementation of it. Right now it only creates pull requests and lists
issues.
Restructued some code. Idk if it will be permanent.
Next I plan to add behavior around replacing files in the local repo,
and creating commits.