[Docs] Add app logo to main page + cleanup (#7471)

* Add app logo to main page

* rename pages folder

* Add link + cleanup

* Cleanup file extension patterns

* Update Doxygen README.md

doc/doxygen/extra-pages/user_documentation/deck_management/creating_decks.md

@@ -1,15 +0,0 @@
-@page creating_decks Creating Decks
-
-Creating a new deck is done using either the \ref editing_decks_classic or \ref editing_decks_visual.
-
-They can be accessed either by clicking the "Create Deck" button in the TabHome screen, which will open the default deck
-editor configured in the "User Interface" -> "Deck editor/storage settings" -> "Default deck editor type" setting, or
-by selecting "Deck Editor" or "Visual Deck Editor" under the "Tabs" application menu located at the top.
-
-# Further References
-
-- See @ref editing_decks for information on how to modify the attributes and contents of a deck in the Deck Editor
-widgets.
-- See @ref exporting_decks for information on how to store and persist your deck either in-client or to external
-services.
-- See @ref importing_decks for information on how to import existing decks either in-client or from external services