[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/pages/user_documentation/deck_management/creating_decks.md

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+@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