add: 文字透明背景

packages/webview/src/components/Signatures/SignCreatePanel.vue

@@ -113,7 +113,7 @@ const save = (evt) => {
     ctx = canvasDraw.getContext("2d")
 
     ctx.font = "46px  Segoe UI"
-    ctx.fillStyle = "white"
+    ctx.fillStyle = "transparent"
     ctx.fillRect(0, 0, textWidth, 60)
     ctx.fillStyle = "black"
     ctx.fillText(textSgin.value, 0, 50)