feat(frontend): add french language file

also expanded translation coverage (still lots to do!)

src/components/Layout/LanguagePicker/index.tsx

@@ -25,6 +25,10 @@ const availableLanguages: AvailableLanguageObject = {
     code: 'ja',
     display: '日本語',
   },
+  fr: {
+    code: 'fr',
+    display: 'Français',
+  },
 };
 
 const LanguagePicker: React.FC = () => {

src/components/Layout/UserDropdown/index.tsx

@@ -3,6 +3,11 @@ import Transition from '../../Transition';
 import { useUser } from '../../../hooks/useUser';
 import axios from 'axios';
 import useClickOutside from '../../../hooks/useClickOutside';
+import { defineMessages, FormattedMessage } from 'react-intl';
+
+const messages = defineMessages({
+  signout: 'Sign Out',
+});
 
 const UserDropdown: React.FC = () => {
   const dropdownRef = useRef<HTMLDivElement>(null);
@@ -56,7 +61,7 @@ const UserDropdown: React.FC = () => {
               role="menuitem"
               onClick={() => logout()}
             >
-              Sign out
+              <FormattedMessage {...messages.signout} />
             </a>
           </div>
         </div>

src/components/Layout/index.tsx

@@ -5,6 +5,12 @@ import Sidebar from './Sidebar';
 import Notifications from './Notifications';
 import LanguagePicker from './LanguagePicker';
 import { useRouter } from 'next/router';
+import { defineMessages, FormattedMessage } from 'react-intl';
+
+const messages = defineMessages({
+  alphawarning:
+    'This is ALPHA software. Almost everything is bound to be nearly broken and/or unstable. Please report issues to the Overseerr Github!',
+});
 
 const Layout: React.FC = ({ children }) => {
   const [isSidebarOpen, setSidebarOpen] = useState(false);
@@ -70,9 +76,7 @@ const Layout: React.FC = ({ children }) => {
                     </div>
                     <div className="ml-3 flex-1 md:flex md:justify-between">
                       <p className="text-sm leading-5 text-white">
-                        This is ALPHA software. Almost everything is bound to be
-                        nearly broken or unstable. Please report issues to the
-                        Overseerr Github!
+                        <FormattedMessage {...messages.alphawarning} />
                       </p>
                       <p className="mt-3 text-sm leading-5 md:mt-0 md:ml-6">
                         <a