Extract session translation strings

lib/music_library_web/controllers/session_html/new.html.heex

@@ -2,13 +2,13 @@
   <div class="w-full max-w-sm space-y-10">
     <div>
       <h2 class="mt-10 text-center text-2xl font-bold leading-9 tracking-tight text-gray-900">
-        Welcome to your Music Library
+        <%= gettext("Welcome to your Music Library") %>
       </h2>
     </div>
     <.form class="space-y-6" for={@form} action={~p"/sessions/create"}>
       <div class="relative -space-y-px rounded-md shadow-sm">
         <div>
-          <label for="password" class="sr-only">Password</label>
+          <label for="password" class="sr-only"><%= gettext("Password") %></label>
           <input
             id="password"
             name="password"
@@ -26,7 +26,7 @@
           type="submit"
           class="flex w-full justify-center rounded-md bg-indigo-600 px-3 py-1.5 text-sm font-semibold leading-6 text-white hover:bg-indigo-500 focus-visible:outline focus-visible:outline-2 focus-visible:outline-offset-2 focus-visible:outline-indigo-600"
         >
-          Sign in
+          <%= gettext("Sign in") %>
         </button>
       </div>
     </.form>