Mypy-json-report

- *Action required:* Move existing behaviour under "parse" subcommand.
Invocations of `mypy-json-report` should now be replaced with `mypy-json-report parse`.
- Add `parse --indentation` flag to grant control over how much indentation is used in the JSON report.
- Add `parse --output-file` flag to allow sending report direct to a file rather than STDOUT.
- Add `parse --diff-old-report` flag for a report of the difference since the last JSON report.
- Use GA version of Python 3.11 in test matrix.

- Removed upper bound for Python compatibility
- Add Python 3.11 to test matrix

- Trial releasing with GitHub actions.

- Trial releasing with GitHub actions.

- Create initial project.