feat(Ad): Add DOM button to export PDF

closes #384

src/app/content.ts

@@ -1,14 +1,10 @@
-import {getState, StateType} from './state/get-state';
+import {getState} from './state/get-state';
 import {initializeState} from './state/initialize-state';
 import {setState, StateKeys} from './state/set-state';
 import {Ad} from './ad/ad';
+import {addContentButton} from './utils/add-content-button';
 
-/**
- * Content script entry point.
- *
- * @returns {Promise<StateType>} - The state of the extension.
- */
-export async function content(): Promise<StateType> {
+export async function content(): Promise<void> {
   await initializeState();
   const state = await getState();
 
@@ -22,7 +18,7 @@ export async function content(): Promise<StateType> {
     }
   }
 
-  return state;
+  addContentButton();
 }
 
 window.addEventListener('load', content);

src/app/utils/add-content-button.ts

@@ -0,0 +1,16 @@
+import {StateKeys, setState} from '../state/set-state';
+
+export function addContentButton() {
+  const container = document.querySelector('.mt-xl');
+  const button = document.createElement('button');
+  button.id = 'export';
+  button.textContent = 'Export PDF';
+  button.className =
+    'u-shadow-border-transition box-border inline-flex items-center justify-center gap-md whitespace-nowrap px-lg text-body-1 font-bold focus-visible:outline-none focus-visible:u-ring [&:not(:focus-visible)]:ring-inset bg-transparent border-sm border-current min-w-sz-44 h-sz-44 rounded-lg hover:bg-support/dim-5 enabled:active:bg-support/dim-5 focus-visible:bg-support/dim-5 text-support w-full';
+
+  button.onclick = async () => {
+    await setState(StateKeys.isTriggered, true);
+  };
+
+  container.appendChild(button);
+}