Output warning if detected blocking local resources while rendering by Chrome

[yhatt]

I've received many feedbacks about rendering the local image file, "Image does not see on rendered PDF". In most cases, a cause is lacking --allow-local-files option.

Accessing the local content is often targeted as a vulnerability, so the user must express intention by the option. However, Marp CLI has not explained this while converting.

It's good to tell that it might lack --allow-local-files option if detected blocking access to the local file. Of course, we should keep in mind that it's just a hint and must keep not to recommend.

How to detect

We don't yet try for detection, but I wonder if Chrome outputs any warnings with its reason when blocked loading image. We should listen to Chrome error through Puppeteer, and detect local file access.

[yhatt]

A list of similar feedbacks and responses

• PDF not being rendered with background image marp-core#54 (comment)
• center image marpit#141 (comment)
• Lose img via marp command #96 (comment)