Add macOS-specific test surface creation and adjust imports

Introduced a macOS-specific `create_test_surface` function in `plotly_kaleido` and adjusted test-related imports in `plotly`. Ensures compatibility with macOS while keeping non-macOS logic intact.

Author: joaquinbejar

plotly/src/plot.rs

@@ -584,12 +584,12 @@ impl PartialEq for Plot {
 
 #[cfg(test)]
 mod tests {
-    use serde_json::{json, to_value};
-    use std::path::PathBuf;
-
     use super::*;
     use crate::Scatter;
-
+    #[cfg(not(target_os = "macos"))]
+    use base64::engine::general_purpose;
+    use serde_json::{json, to_value};
+    use std::path::PathBuf;
     fn create_test_plot() -> Plot {
         let trace1 = Scatter::new(vec![0, 1, 2], vec![6, 10, 2]).name("trace1");
         let mut plot = Plot::new();

plotly_kaleido/src/lib.rs

@@ -300,6 +300,7 @@ mod tests {
         .unwrap()
     }
 
+    #[cfg(target_os = "macos")]
     fn create_test_surface() -> Value {
         to_value(json!({
             "data": [