Add editor config option

Ref T677

config/config.go

@@ -64,6 +64,7 @@ type (
 
 		// Site appearance
 		Theme      string `ini:"theme"`
+		Editor     string `ini:"editor"`
 		JSDisabled bool   `ini:"disable_js"`
 		WebFonts   bool   `ini:"webfonts"`
 		Landing    string `ini:"landing"`

pad.go

@@ -53,7 +53,10 @@ func handleViewPad(app *App, w http.ResponseWriter, r *http.Request) error {
 		}
 	}
 
-	padTmpl := "pad"
+	padTmpl := app.cfg.App.Editor
+	if padTmpl == "" {
+		padTmpl = "pad"
+	}
 
 	if action == "" && slug == "" {
 		// Not editing any post; simply render the Pad