"Core" lint in lint-staged mishandles staged file filtering

[luxaritas]

• When the micromatch matches none of the staged files, the eslint command is still run and is run on all files. It shouldn't run at all
• We have a rule for package.json, but it isn't being included in the matcher
• We may not need to do that filtering at all if we pass --no-error-on-unmatched-pattern when calling eslint