Release 15.0.0-esm.0

• Refactor plugin loader + tests (remove proxyquire) (570e349)
• Fix ava config (ad03f71)
• Fix imports in tests (e7e664c)
• Fix lodash import (7ab8574)
• Fix relative import paths (f28ec24)
• Add .js extension to imports (c31548c)
• Use util to read JSON (216267b)
• Format modules (eeb4126)
• Update package.json + .eslintrc.json (abd3c73)
• Convert CommonJS to ES Modules (179708a)
• Update dependencies (0568d3e)
• Only trim end of stdout (75d0c2f)