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

• 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

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

[biiibooo]

👋 @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

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[codecov]

Codecov Report

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

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

@@           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	Coverage Δ
src/util.ts	60.86% <ø> (ø)
src/clone-node.ts	75.92% <50.00%> (ø)
src/embed-images.ts	81.81% <83.33%> (ø)

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[DustinBrett]

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.

[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.