Add error reporter

[DonIsaac]

Add an error reporter struct/thing responsible for ingesting linter/semantic/parse errors and printing them using one of several formats.

Acceptance Criteria

• Support plugging in a formatted. This will be used to support pretty/colorful outputs, github actions outputs, and a JSON format that can be integrated into a VSCode plugin
• Should print to an io.Writer. Will often be stdout, but I'd like to support writing directly to a file or TCP socket.
• Must be thread-safe

[DonIsaac]

55

[DonIsaac]

This is missing features but it's mostly there. At least enough to be usable. Closing as completed.