ImGui: Add TTF font support

We use the Roboto font that we're already shipping for now, although, we could
also support other fonts or have a setting.

UI/ImDebugger/ImDebugger.cpp

@@ -399,7 +399,8 @@ void ImDebugger::Frame(MIPSDebugInterface *mipsDebug, GPUDebugInterface *gpuDebu
 			if (ImGui::MenuItem("Close Debugger")) {
 				g_Config.bShowImDebugger = false;
 			}
-			ImGui::MenuItem("Dear ImGUI Demo", nullptr, &cfg_.demoOpen);
+			ImGui::MenuItem("Dear ImGui Demo", nullptr, &cfg_.demoOpen);
+			ImGui::MenuItem("Dear ImGui Style editor", nullptr, &cfg_.styleEditorOpen);
 			ImGui::EndMenu();
 		}
 		ImGui::EndMainMenuBar();
@@ -409,6 +410,10 @@ void ImDebugger::Frame(MIPSDebugInterface *mipsDebug, GPUDebugInterface *gpuDebu
 		ImGui::ShowDemoWindow(&cfg_.demoOpen);
 	}
 
+	if (cfg_.styleEditorOpen) {
+		ImGui::ShowStyleEditor();
+	}
+
 	if (cfg_.disasmOpen) {
 		disasm_.Draw(mipsDebug, &cfg_.disasmOpen, coreState);
 	}