feat: add maxBodyLength parameter to htmlToMarkdown

[yellowtailfan]

Supporting change for fixing Expensify/App#57241.

Tests

1. What unit/integration tests cover your change? What autoQA tests cover your change?

• Added "Test long HTML header" to __tests__/ExpensiMark-Markdown-test.js

2. What tests did you perform that validates your changed worked?

• Tested on all platforms from App code modified to use new maxBodyLength parameter.
• Tests include HTML clipboard paste on platforms where available.
• Tests included very large clipboard pastes to check for performance issues. There was some lag but it was similar both before and after this change.
• Inspected all calls to htmlToMarkdown() from Expensify repo and none will be affected by the additional parameter.

QA

1. What does QA need to do to validate your changes?

• Run unit tests.

2. What areas to they need to test for regressions?

• HTML to Markdown conversion.

[github-actions]

All contributors have signed the CLA ✍️ ✅
_{Posted by the CLA Assistant Lite bot.}

[yellowtailfan]

I have read the CLA Document and I hereby sign the CLA

[inimaga]

LGTM

[os-botify]

🚀 Published to npm in 2.0.136 🎉

[jjcoffee]

Coming from Expensify/App#63711. We should have decoded the HTML first before truncation, otherwise decoding can fail if there isn't enough content to decode. More details here.

[yellowtailfan]

Thanks for your feedback. The reason we truncated early was a compromise: there were serious performance issues with parsing into Markdown before truncation. I'll find a reference for you.

[yellowtailfan]

Here is a more detailed comment on the performance issues around truncation before or after parsing: Expensify/App#57241 (comment)

[yellowtailfan]

Here is a summary of our investigation: Expensify/App#57241 (comment) and the accepted proposal Expensify/App#57241 (comment)