Update plugins to support standalone components

- ThemedComponent wrappers should always import their base component. This ensures that it's always enough to only import the wrapper when we use it.
- This implies that all themeable components must be standalone

→ added rules to enforce this
→ updated usage rule to improve declaration/import handling

lint/src/rules/ts/index.ts

@@ -10,12 +10,14 @@ import {
   RuleExports,
 } from '../../util/structure';
 /* eslint-disable import/no-namespace */
+import * as themedComponentClasses from './themed-component-classes';
 import * as themedComponentSelectors from './themed-component-selectors';
 import * as themedComponentUsages from './themed-component-usages';
 
 const index = [
-  themedComponentUsages,
+  themedComponentClasses,
   themedComponentSelectors,
+  themedComponentUsages,
 ] as unknown as RuleExports[];
 
 export = {