feat(theme,interfaces): Introduce a global theming system and unify menu/tab interfaces; migrate components to use themeDefaultStyles and update APIs accordingly

ts_web/elements/dees-heading/dees-heading.ts

@@ -11,6 +11,7 @@ import {
 
 import { demoFunc } from './dees-heading.demo.js';
 import { cssCalSansFontFamily } from '../00fonts.js';
+import { themeDefaultStyles } from '../00theme.js';
 
 declare global {
   interface HTMLElementTagNameMap {
@@ -32,8 +33,10 @@ export class DeesHeading extends DeesElement {
 
   // STATIC STYLES
   public static styles: CSSResult[] = [
+    themeDefaultStyles,
     cssManager.defaultStyles,
     css`
+      /* TODO: Migrate hardcoded values to --dees-* CSS variables */
       /* Heading styles */
       h1, h2, h3, h4, h5, h6 {
         margin: 16px 0 8px;