feat: add opt-in trailing whitespace highlighting

src/editor.rs

@@ -1763,6 +1763,7 @@ pub struct Editor {
     popup: PopupConfig,
     labels: BTreeMap<String, String>,
     scroll_distance: Option<usize>,
+    highlight_trailing_whitespace: bool,
     battery_charge: Option<u8>,
     battery_label: String,
     git_blame: bool,
@@ -1865,6 +1866,7 @@ impl Editor {
             popup: PopupConfig::default(),
             labels: BTreeMap::new(),
             scroll_distance: Some(0),
+            highlight_trailing_whitespace: false,
             battery_charge: None,
             battery_label: String::new(),
             git_blame: true,
@@ -2611,6 +2613,14 @@ impl Editor {
         self.scroll_distance = distance;
     }
 
+    pub(crate) fn highlight_trailing_whitespace(&self) -> bool {
+        self.highlight_trailing_whitespace
+    }
+
+    pub(crate) fn set_highlight_trailing_whitespace(&mut self, enabled: bool) {
+        self.highlight_trailing_whitespace = enabled;
+    }
+
     pub(crate) fn set_diff_context_options(&mut self, context_lines: usize, expand_lines: usize) {
         self.diff_context_options = (context_lines, expand_lines);
         if let Some(diff) = &mut self.diff {