feat(dees-element): add container-responsive APIs (containerResponsive decorator, DeesElement static cssFor* container helpers, and cssManager cssForCustom) and update docs

ts/decorators.containerresponsive.ts

@@ -0,0 +1,19 @@
+import * as domtools from '@design.estate/dees-domtools';
+
+export function containerResponsive() {
+  return function (target: any) {
+    const tagName: string =
+      target.is || target.name.replace(/([a-z])([A-Z])/g, '$1-$2').toLowerCase();
+    const containerStyles = domtools.breakpoints.containerContextStyles(tagName);
+
+    const original = target.styles;
+    if (Array.isArray(original)) {
+      target.styles = [...original, containerStyles];
+    } else if (original) {
+      target.styles = [original, containerStyles];
+    } else {
+      target.styles = [containerStyles];
+    }
+    return target;
+  };
+}