refactor: name configurable viewport scroll steps accurately

src/ruby_config.rb

@@ -145,7 +145,7 @@ module Vamp
       @popup = PopupConfig.new
       @labels = {}
       @scroll_distance = 0
-      @scroll_half_page_lines = nil
+      @scroll_step_lines = nil
       @highlight_trailing_whitespace = false
       @whitespace_characters = {}
       @whitespace_scope = "all"
@@ -232,8 +232,8 @@ module Vamp
 
     # @param lines [Integer, nil] positive screen rows, or nil for half the viewport
     # @return [Integer, nil]
-    def scroll_half_page_lines=(lines)
-      @scroll_half_page_lines = lines.nil? ? nil : diff_line_count!(lines, "scroll_half_page_lines", 1)
+    def scroll_step_lines=(lines)
+      @scroll_step_lines = lines.nil? ? nil : diff_line_count!(lines, "scroll_step_lines", 1)
     end
 
     # @param enabled [Boolean]
@@ -350,7 +350,7 @@ module Vamp
         "git_blame" => @git_blame,
         "git_gutter" => @git_gutter,
         "scroll_distance" => @scroll_distance,
-        "scroll_half_page_lines" => @scroll_half_page_lines,
+        "scroll_step_lines" => @scroll_step_lines,
         "highlight_trailing_whitespace" => @highlight_trailing_whitespace,
         "whitespace_characters" => @whitespace_characters,
         "whitespace_scope" => @whitespace_scope,