Prettier 2: Electric Boogaloo (#6113)

# Description of Changes
When I added Prettier formatting in #6052, my aim was to use just the
default settings in Prettier. Turns out, Prettier looks _really hard_
for any config files if it's not explicitly given one, which means that
if a developer has some sort of Prettier config file lying around on
their system, Prettier might find it and use it. Also, Prettier changes
its defaults based on stuff in `.editorconfig` without any good way of
disabling that behaviour explicitly in its config file.

To solve both of these issues, I've introduced a `.prettierrc` file
which sets Prettier's defaults explicitly, and then reformatted all our
code _again_ in Prettier's actual default settings. This should achieve
the aim of #6052 and remove the possibility for it breaking on different
dev computers.

frontend/src/saas/components/auth/GuestUserBanner.tsx

@@ -50,10 +50,16 @@ export function GuestUserBanner({ className = "" }: GuestUserBannerProps) {
   };
 
   return (
-    <div className={`guest-banner ${className || ""}`} role="status" aria-live="polite">
+    <div
+      className={`guest-banner ${className || ""}`}
+      role="status"
+      aria-live="polite"
+    >
       <div className="guest-banner-content">
         <div className="guest-banner-text">
-          <div className="guest-banner-title">{t("guestBanner.title", "You're using Stirling PDF as a guest!")}</div>
+          <div className="guest-banner-title">
+            {t("guestBanner.title", "You're using Stirling PDF as a guest!")}
+          </div>
           <div className="guest-banner-message">
             {t(
               "guestBanner.message",