🔧 add `.spyglassrc.json` and exclude patterns

[TheAfroOfDoom]

Summary

this will prevent:

• the build directory from being parsed on project load
• our MC unit tests from raising IDE errors falsely (since they use modded commands from packtest)
• note all this requires being on my custom spyglass branch until it's merged:

https://github.com/TheAfroOfDoom/Spyglass/tree/watcher-ignore-exclude-config

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overall generally much faster Spyglass load times, and probably faster performance in general since we're not watching nearly as many files