fix: iframe content displayed incorrectly

[haodaking]

This pull request addresses the issue with capturing iframes in the library, where the resulting images were blank or incorrect.

Description

https://stackoverflow.com/questions/26248599/instanceof-htmlelement-in-iframe-is-not-element-or-object

Motivation and Context

Types of changes

• [x] Bug fix (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 change)
• [ ] Enhancement (changes that improvement of current feature or performance)
• [ ] Refactoring (changes that neither fixes a bug nor adds a feature)
• [ ] Test Case (changes that add missing tests or correct existing tests)
• [ ] Code style optimization (changes that do not affect the meaning of the code)
• [ ] Docs (changes that only update documentation)
• [ ] Chore (changes that don't modify src or test files)

Self Check before Merge

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [ ] All new and existing tests passed.

[vivcat[bot]]

👋 @haodaking

💖 Thanks for opening this pull request! 💖

Please follow the contributing guidelines. And we use semantic commit messages to streamline the release process.

Examples of commit messages with semantic prefixes:

• fix: don't overwrite prevent_default if default wasn't prevented
• feat: add graph.scale() method
• docs: graph.getShortestPath is now available

Things that will help get your PR across the finish line:

• Follow the TypeScript coding style.
• Run npm run lint locally to catch formatting errors earlier.
• Document any user-facing changes you've made.
• Include tests when adding/changing behavior.
• Include screenshots and animated GIFs whenever possible.

We get a lot of pull requests on this repo, so please be patient and we will get back to you as soon as we can.

[codecov[bot]]

Codecov Report

Base: 63.24% // Head: 63.24% // No change to project coverage :thumbsup:

Coverage data is based on head (130f2f9) compared to base (7a83b54). Patch coverage: 60.00% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #351 +/- ## ======================================= Coverage 63.24% 63.24% ======================================= Files 10 10 Lines 555 555 Branches 129 129 ======================================= Hits 351 351 Misses 146 146 Partials 58 58 ``` | [Impacted Files](https://codecov.io/gh/bubkoo/html-to-image/pull/351?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=%E5%B4%96) | Coverage Δ | | |---|---|---| | [src/util.ts](https://codecov.io/gh/bubkoo/html-to-image/pull/351/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=%E5%B4%96#diff-c3JjL3V0aWwudHM=) | `60.86% <ø> (ø)` | | | [src/clone-node.ts](https://codecov.io/gh/bubkoo/html-to-image/pull/351/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=%E5%B4%96#diff-c3JjL2Nsb25lLW5vZGUudHM=) | `75.92% <50.00%> (ø)` | | | [src/embed-images.ts](https://codecov.io/gh/bubkoo/html-to-image/pull/351/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=%E5%B4%96#diff-c3JjL2VtYmVkLWltYWdlcy50cw==) | `81.81% <83.33%> (ø)` | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=%E5%B4%96). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=%E5%B4%96)

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[DustinBrett]

Thanks for this PR and finding the core issues. I've decided to make my own PR (https://github.com/bubkoo/html-to-image/pull/352) as I feel in some ways I've introduced this issue. I am not sure on the etiquette of conflicting PR's in open source. Sorry if I stepped on toes but I prefer to create my own PR in this case. I felt the tagName approach although effective could maybe be adjusted to use something more generic, and I also didn't see a need for a few other changes in the PR. So I made mine to focus on what I considered required to complete my original PR where I claimed to add iframes as a whole.

[haodaking]

Thanks for this PR and finding the core issues. I've decided to make my own PR (#352) as I feel in some ways I've introduced this issue. I am not sure on the etiquette of conflicting PR's in open source. Sorry if I stepped on toes but I prefer to create my own PR in this case. I felt the tagName approach although effective could maybe be adjusted to use something more generic, and I also didn't see a need for a few other changes in the PR. So I made mine to focus on what I considered required to complete my original PR where I claimed to add iframes as a whole.

Thank you, I think your code implementation is more elegant and learning.