Meta: add infrastructure to generate summary.json

The setup is as follows: 1. We collect all the issue data from the repository through the GitHub API and store it in a JSON file. Storing the input allows us to monitor changes in it for bugs. We'll likely want to change some issues so they are more suitable for consumption by the script. 2. The script takes this data and produces a JSON file with a summarized view of each issue. The bulk of the logic is in processing the body of the issue (the top comment) which is split between before and after the YAML change. The idea is that the JSON file with the summarized view can be consumed and eventually displayed on webkit.org once we're happy with it. It currently has some flaws due to the raw data, but it seems worthwhile to check this in and then improve the raw data to validate the entire process around updating the issue data.