feat(xml): add spinbox support (#8957)

Co-authored-by: Liam Howatt <30486941+liamHowatt@users.noreply.github.com>

tests/src/test_cases/xml/test_xml_spinbox.c

@@ -0,0 +1,35 @@
+#if LV_BUILD_TEST
+#include "../lvgl.h"
+
+#include "unity/unity.h"
+
+void setUp(void)
+{
+    /* Function run before every test */
+}
+
+void tearDown(void)
+{
+    /* Function run after every test */
+    lv_obj_clean(lv_screen_active());
+}
+
+void test_spinbox_with_attrs(void)
+{
+    lv_obj_t * scr = lv_screen_active();
+
+    const char * attrs_1[] = {
+        "min_value", "0",
+        "max_value", "3000",
+        "digit_count", "5",
+        "dec_point_pos", "3",
+        "value", "1234",
+        "align", "center",
+        NULL, NULL,
+    };
+
+    lv_xml_create(scr, "lv_spinbox", attrs_1);
+    TEST_ASSERT_EQUAL_SCREENSHOT("xml/lv_spinbox.png");
+}
+
+#endif