fix: add possibility to use own handling of onerror which will not en…

[misino]

…d up in the exception

Description

Motivation and Context

We had a problem with generating an image when html contained pictures with src pointing to a domain which doesn't allow CORS.
This change is about possibility to specify own onerror callback which don't need to make whole image generation fail.

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.

[vivcat]

👋 @misino

💖 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]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (b751cbf) 62.93% compared to head (3b6fd62) 63.10%.
Report is 11 commits behind head on master.

Files	Patch %	Lines
src/embed-images.ts	50.00%	1 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #453      +/-   ##
==========================================
+ Coverage   62.93%   63.10%   +0.17%     
==========================================
  Files          10       10              
  Lines         580      580              
  Branches      143      143              
==========================================
+ Hits          365      366       +1     
  Misses        151      151              
+ Partials       64       63       -1     

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