theme: make dracula ui.virtual.whitespace less intrusive (#5627)

runtime/themes/dracula.toml

@@ -40,7 +40,7 @@
 "ui.text" = { fg = "foreground" }
 "ui.text.focus" = { fg = "cyan" }
 "ui.window" = { fg = "foreground" }
-"ui.virtual.whitespace" = { fg = "comment" }
+"ui.virtual.whitespace" = { fg = "subtle" }
 "ui.virtual.ruler" = { bg = "background_dark"}
 
 "error" = { fg = "red" }
@@ -64,6 +64,7 @@ background = "#282a36"
 background_dark = "#21222c"
 primary_highlight = "#800049"
 secondary_highlight = "#4d4f66"
+subtle = "#424450"
 foreground = "#f8f8f2"
 comment = "#6272a4"
 red = "#ff5555"
@@ -73,3 +74,4 @@ green = "#50fa7b"
 purple = "#bd93f9"
 cyan = "#8be9fd"
 pink = "#ff79c6"
+