Automatically format YAML, CSS, and JS files (#1272)

Initially, I also formatted the templates in `theme/`, but this triggers
https://github.com/prettier/prettier/issues/11834. So I exclude them for
now.

---------

Co-authored-by: Ming-Ying Chung <mych@chromium.org>

theme/css/language-picker.css

@@ -3,7 +3,7 @@
   right: 10px;
 }
 
-[dir=rtl] #language-list {
+[dir="rtl"] #language-list {
   left: 10px;
   right: auto;
 }

theme/speaker-notes.js

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-(function() {
+(function () {
   let notes = document.querySelector("details");
   // Create an unattached DOM node for the code below.
   if (!notes) {
@@ -32,7 +32,7 @@
 
   // Update the window. This shows/hides controls as necessary for regular and
   // speaker note pages.
-  function applyState()  {
+  function applyState() {
     if (window.location.hash == "#speaker-notes-open") {
       if (getState() != "popup") {
         markDefunct();
@@ -116,9 +116,11 @@
         setState("popup");
         applyState();
       } else {
-        window.alert("Could not open popup, please check your popup blocker settings.");
+        window.alert(
+          "Could not open popup, please check your popup blocker settings."
+        );
       }
-    })
+    });
     let popOutIcon = document.createElement("i");
     popOutIcon.classList.add("fa", "fa-external-link");
     popOut.append(popOutIcon);
@@ -179,9 +181,11 @@
     }
 
     // Update prev/next buttons to keep speaker note state.
-    document.querySelectorAll('a[rel="prev"], a[rel="next"]').forEach((elem) => {
-      elem.href += "#speaker-notes-open";
-    });
+    document
+      .querySelectorAll('a[rel="prev"], a[rel="next"]')
+      .forEach((elem) => {
+        elem.href += "#speaker-notes-open";
+      });
   }
 
   let timeout = null;