Custom ESLint rules to enforce new ThemedComponent selector convention

The following cases are covered:
- ThemedComponent wrapper selectors must not start with ds-themed-
- Base component selectors must start with ds-base-
- Themed component selectors must start with ds-themed-
- The ThemedComponent wrapper must always be used in HTML
- The ThemedComponent wrapper must be used in TypeScript _where appropriate_:
  - Required
    - Explicit usages (e.g. modal instantiation, routing modules, ...)
    - By.css selector queries (in order to align with the HTML rule)
  - Unchecked
    - Non-routing modules (to ensure the components can be declared)
    - ViewChild hooks (since they need to attach to the underlying component)

All rules work with --fix to automatically migrate to the new convention
This covers most of the codebase, but minor manual adjustment are needed afterwards

lint/src/rules/ts/index.ts

@@ -0,0 +1,9 @@
+import themedComponentSelectors from './themed-component-selectors';
+import themedComponentUsages from './themed-component-usages';
+
+export = {
+  rules: {
+    'themed-component-selectors': themedComponentSelectors,
+    'themed-component-usages': themedComponentUsages,
+  },
+};