Actually add Doxygen main page

I apparently forgot to add this file in my previous commit (bd40ee2b95138139a8cfbef878b3461176688c15).

diff --git a/doc/main_page.dox b/doc/main_page.dox
new file mode 100644 (file)
index 0000000..8211d9c
--- /dev/null
+++ b/doc/main_page.dox
@@ -0,0 +1,8 @@
+/** @mainpage The Minetest engine internal documentation
+
+Welcome to the Minetest engine Doxygen documentation site!\n
+This page documents the internal structure of the Minetest engine's C++ code.\n
+Use the tree view at the left to navigate.
+
+*/
+