Added memory FS and put the default font there so it is easier to load it.

public/raid/raid.hpp

@@ -10,6 +10,7 @@
 #include <imgui.h>
 #include <mijin/async/coroutine.hpp>
 #include <mijin/util/bitflags.hpp>
+#include <mijin/virtual_filesystem/memory.hpp>
 #include <mijin/virtual_filesystem/stacked.hpp>
 #include <SDL3/SDL.h>
 
@@ -21,6 +22,7 @@ inline constexpr ImGuiWindowFlags DEFAULT_MAIN_WINDOW_FLAGS = 0
                                 | ImGuiWindowFlags_NoDecoration
                                 | ImGuiWindowFlags_NoBringToFrontOnFocus
                                 | ImGuiWindowFlags_NoNav;
+inline constexpr const char* DEFAULT_FONT_PATH = "/data/fonts/NotoSans-Regular.ttf";
 
 enum class MessageSeverity : unsigned char
 {
@@ -55,6 +57,7 @@ private:
     SDL_GLContext mGLContext = nullptr;
 
     mijin::StackedFileSystemAdapter mFS;
+    mijin::MemoryFileSystemAdapter* mMemoryFS = nullptr;
     mijin::SimpleTaskLoop mTaskLoop;
     std::unordered_map<fs::path, ImTextureID> mTextures;
 
@@ -91,6 +94,13 @@ public:
     [[nodiscard]]
     mijin::StackedFileSystemAdapter& getFS() { return mFS; }
 
+    [[nodiscard]]
+    mijin::MemoryFileSystemAdapter& getMemoryFS()
+    {
+        MIJIN_ASSERT_FATAL(mMemoryFS != nullptr, "Memory FS has not been initialized yet.");
+        return *mMemoryFS;
+    }
+
     [[nodiscard]]
     mijin::SimpleTaskLoop& getLoop() { return mTaskLoop; }