Revert "use global namespace"

This reverts commit 24c3a9abd3.

# Conflicts:
#	packages/core/src/Editor.ts

.eslintrc.js

@@ -70,8 +70,6 @@ module.exports = {
         '@typescript-eslint/ban-types': 'off',
         '@typescript-eslint/comma-dangle': ['error', 'always-multiline'],
         '@typescript-eslint/explicit-module-boundary-types': 'off',
-        '@typescript-eslint/no-namespace': 'off',
-        'no-undef': 'off',
       },
     },
   ],