Migrate action, common, a11y translation keys

```
move () {
  FROM=$1 TO=$2 find public/locales -type f -exec sh -c 'jq ".$TO = .\"$FROM\" | del(.\"$FROM\") | del(..|nulls) | select(length > 0)" {} | sponge {}' \;
}

move "Avatar" "common.avatar"
move "Camera" "common.camera"
move "Close" "action.close"
move "Copied!" "common.copied"
move "Copy" "action.copy"
move "Copy link" "action.copy_link"
move "Encrypted" "common.encrypted"
move "Go" "action.go"
move "Home" "common.home"
move "Invite" "action.invite"
move "Loading…" "common.loading"
move "Microphone" "common.microphone"
move "No" "action.no"
move "Not encrypted" "common.unencrypted"
move "Password" "common.password"
move "Profile" "common.profile"
move "Username" "common.username"
move "Video" "common.video"
move "Register" "action.register"
move "Remove" "action.remove"
move "Settings" "common.settings"
move "Sign in" "action.sign_in"
move "Sign out" "action.sign_out"
move "Submit" "action.submit"
move "User menu" "a11y.user_menu"
move "Audio" "common.audio"
move "Display name" "common.display_name"
```

src/room/GroupCallLoader.tsx

@@ -54,7 +54,7 @@ export function GroupCallLoader({
     case "loading":
       return (
         <FullScreenView>
-          <h1>{t("Loading…")}</h1>
+          <h1>{t("common.loading")}</h1>
         </FullScreenView>
       );
     case "loaded":
@@ -72,7 +72,7 @@ export function GroupCallLoader({
             {/* XXX: A 'create it for me' button would be the obvious UX here. Two screens already have
             dupes of this flow, let's make a common component and put it here. */}
             <Link href="/" onClick={onHomeClick}>
-              {t("Home")}
+              {t("common.home")}
             </Link>
           </FullScreenView>
         );