docs(site): note fn+F2 on mac

docs/_layouts/default.html

@@ -55,7 +55,7 @@
 	              class="theme-toggle"
 	              type="button"
 	              data-theme-toggle
-              aria-label="Toggle theme (F2)"
+	              aria-label="Toggle theme (F2; on Mac: fn+F2)"
 	              aria-pressed="false"
 	            >
 	              <span class="theme-toggle__key">F2</span>
@@ -125,7 +125,8 @@
             <a href="https://www.npmjs.com/package/clawdis">npm</a>
 	          </div>
 	          <div class="footer__hint" aria-hidden="true">
-            tip: press <kbd>F2</kbd> to flip the universe
+	            tip: press <kbd>F2</kbd> (Mac: <kbd>fn</kbd>+<kbd>F2</kbd>) to flip
+	            the universe
 	          </div>
 	        </footer>
 	      </div>