fix: Various editor / diagnostic improvements (#2363)

- Closes: #2360 
 - Closes: #2328

src/ha/side-load-ha-elements.ts

@@ -22,7 +22,6 @@ export const sideLoadHomeAssistantElements = async (): Promise<boolean> => {
     'ha-spinner',
     'ha-state-icon',
     'ha-web-rtc-player',
-    'mwc-button',
     'mwc-list-item',
     'state-badge',
   ];

src/ha/types.ts

@@ -189,6 +189,7 @@ export interface LovelaceCard extends HTMLElement {
   hass?: HomeAssistant;
   isPanel?: boolean;
   editMode?: boolean;
+  preview?: boolean;
   getCardSize(): number | Promise<number>;
   setConfig(config: LovelaceCardConfig): void;
 }