Refactor dialogs, make it simple to add a new dialog to all views

ui/src/dialogs/Dialogs.js

@@ -0,0 +1,11 @@
+import { AddToPlaylistDialog } from './AddToPlaylistDialog'
+import DownloadMenuDialog from './DownloadMenuDialog'
+import { HelpDialog } from './HelpDialog'
+
+export const Dialogs = (props) => (
+  <>
+    <AddToPlaylistDialog />
+    <DownloadMenuDialog />
+    <HelpDialog />
+  </>
+)

ui/src/dialogs/index.js

@@ -1,5 +1,4 @@
 export * from './AboutDialog'
-export * from './AddToPlaylistDialog'
 export * from './SelectPlaylistInput'
-export * from './HelpDialog'
 export * from './ListenBrainzTokenDialog'
+export * from './Dialogs'