Add 'scrollbarchar' option (#2342)

This lets you specify a character that will get used for rendering the
scrollbar.

Co-authored-by: Zachary Yedidia <zyedidia@gmail.com>

internal/config/settings.go

@@ -353,6 +353,9 @@ var DefaultGlobalOnlySettings = map[string]interface{}{
 	"multiopen":      "tab",
 	"parsecursor":    false,
 	"paste":          false,
+	"savehistory":    true,
+	"scrollbarchar":  "|",
+	"sucmd":          "sudo",
 	"pluginchannels": []string{"https://raw.githubusercontent.com/micro-editor/plugin-channel/master/channel.json"},
 	"pluginrepos":    []string{},
 	"savehistory":    true,