fix: Image paste from webflow (#3743)

## Description


https://discord.com/channels/955905230107738152/1262723546669645865/1262723682032287838



## Steps for reproduction

1. click button
2. expect xyz

## Code Review

- [ ] hi @kof, I need you to do
  - conceptual review (architecture, feature-correctness)
  - detailed review (read every line)
  - test it on preview

## Before requesting a review

- [ ] made a self-review
- [ ] added inline comments where things may be not obvious (the "why",
not "what")

## Before merging

- [ ] tested locally and on preview environment (preview dev login:
5de6)
- [ ] updated [test
cases](https://github.com/webstudio-is/webstudio/blob/main/apps/builder/docs/test-cases.md)
document
- [ ] added tests
- [ ] if any new env variables are added, added them to `.env` file

apps/builder/app/shared/copy-paste/plugin-webflow/schema.ts

@@ -202,7 +202,7 @@ const WfElementNode = z.union([
     type: z.enum(["Image"]),
     data: WfNodeData.extend({
       attr: Attr.extend({
-        alt: z.string(),
+        alt: z.string().optional(),
         loading: z.enum(["lazy", "eager", "auto"]),
         src: z.string(),
         width: z.string(),