only run bindgen on ImPlot... names

not sure why bindgen switches to i32 everywhere
moved imgui dependency up one step as this seems where its actually used

implot-sys-bindgen/src/main.rs

@@ -34,6 +34,8 @@ fn main() {
         )
         .parse_callbacks(Box::new(CargoCallbacks))
         .clang_arg("-DCIMGUI_DEFINE_ENUMS_AND_STRUCTS=1")
+        .whitelist_function("ImPlot.*")
+        .whitelist_type("ImPlot.*")
         .generate()
         .expect("Unable to generate bindings");