Merge pull request #187 from teunbrand/compat_ggplot2_400

ggplot2 transitioned from S3 class to S7 class, hence affecting several functions including 
```
expect_s3_class(p, "ggplot")
expect_length(p, 11)
expect_type(p, "list")
```
which directly affects the testing script for function add_scaling_component_to_delta_plot(). 
The output of this function is a list, and the first element of the list is a ggplot2 object.

Author: Jacobluke-

DESCRIPTION

@@ -49,7 +49,7 @@ Imports:
     dplyr,
     effsize,
     ggbeeswarm,
-    ggplot2 (>= 3.5.1),
+    ggplot2 (>= 3.5.2),
     ggsci,
     grid,
     magrittr,

tests/testthat/test_002_plot_components.R

@@ -12,7 +12,7 @@ describe("Testing add_scaling_component_to_delta_plot function", {
     expect_type(result, "list")
     expect_equal(length(result), 3) # 3 components returned
     # Check delta_plot component
-    expect_type(result[[1]], "list")
+    expect_true(ggplot2::is_ggplot(result[[1]]))
     # TODO Add specific expectations to check if the components are created correctly
   })
 })