Move primitive wrappers into its own package "imgui.type"

imgui-binding/src/test/java/imgui/ImStringTest.java

@@ -1,5 +1,6 @@
 package imgui;
 
+import imgui.type.ImString;
 import org.junit.jupiter.api.Test;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;