使用分组条形图时如何在R代码中旋转ggplot2中的x轴

install.packages("ggplot2")

library(ggplot2)

df <- data.frame(Group = c("A", "B", "C", "D"),
                 Category = c("Category 1", "Category 2", "Category 3", "Category 4"),
                 Value = c(10, 15, 8, 12))

ggplot(df, aes(x = Group, y = Value, fill = Category)) +
  geom_bar(stat = "identity", position = "dodge") +
  theme(axis.text.x = element_text(angle = 45, hjust = 1))