feat: add opt-in trailing whitespace highlighting

src/ruby_config.rb

@@ -142,6 +142,7 @@ module Vamp
       @popup = PopupConfig.new
       @labels = {}
       @scroll_distance = 0
+      @highlight_trailing_whitespace = false
       @diff_context_lines = 10
       @diff_expand_lines = 15
       @diff_view_mode = "split"
@@ -221,6 +222,14 @@ module Vamp
       @scroll_distance = distance.nil? ? nil : diff_line_count!(distance, "scroll_distance", 0)
     end
 
+    # @param enabled [Boolean]
+    # @return [Boolean]
+    def highlight_trailing_whitespace=(enabled)
+      raise TypeError, "highlight_trailing_whitespace must be true or false" unless [true, false].include?(enabled)
+
+      @highlight_trailing_whitespace = enabled
+    end
+
     # @param lines [Integer] nonnegative context lines around each diff change
     # @return [Integer]
     def diff_context_lines=(lines)
@@ -293,6 +302,7 @@ module Vamp
         "git_blame" => @git_blame,
         "git_gutter" => @git_gutter,
         "scroll_distance" => @scroll_distance,
+        "highlight_trailing_whitespace" => @highlight_trailing_whitespace,
         "top_bar" => @bar.top, "bottom_bar" => @bar.bottom, "labels" => @labels,
         "popup" => { "command" => @popup.command, "search" => @popup.search },
         "diff_context_lines" => @diff_context_lines, "diff_expand_lines" => @diff_expand_lines,