Allow for measuring discussions

[zkoppert]

This pull request allows this action to measure discussion metrics by including type:discussion in the search query. Adding discussions also enables the measurement of the time to answer metric. This will be a breaking change since the .env file has entries removed and so version numbers should roll to 2.0.0.

Tasks:

• Enable the new metric of time to answer
• Wire up existing metrics to handle discussions
• Configure the action to allow for measuring org discussions that are not tied to a repo. Currently this is configured to act on a single repository since issues and pull requests are associated with a repository.
• Update documentation
• Write new tests for the new functions
• Update existing tests for changes to existing functions like write_markdown()

fixes #31

[zkoppert]

Test coverage isn't perfect but its nearly 90%. I'll call that good enough for now and improve later.

[zkoppert]

Still need to merge, bump to v2.0.0 and release. I'm out of office on Monday, so will likely get back to this on Tuesday,