support custom image preview soruce

[chuntungho]

Proposed changes

Support custom image preview source.

Types of changes

What types of changes does your code introduce to Lowcoder?
Put an x in the boxes that apply.

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)

Checklist

You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help!
This is simply a reminder of what we are going to look for before merging your code.
Put an x in the boxes that apply.

• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged and published in downstream modules

Further comments

If this is a relatively large or complex change, kick off the discussion by explaining why you chose the solution you did and what alternatives you considered, etc.

[netlify]

👷 Deploy request for lowcoder-cloud pending review.

Visit the deploys page to approve it

Name	Link
🔨 Latest commit	067ebb5

[FalkWolsky]

这是一个有趣的想法，也是一项了不起的贡献！非常感谢！

[netlify]

👷 Deploy request for lowcoder-test pending review.

Visit the deploys page to approve it

Name	Link
🔨 Latest commit	f136074