feat: add nativeImage.createThumbnailFromPath API

[georgexu99]

Description of Change

This api returns a preview thumbnail of a file given its file path. The thumbnail is the same as a file's preview picture in explorer/finder.

Checklist

• PR description included and stakeholders cc'd
• npm test passes
• tests are changed or added
• relevant documentation is changed or added
• PR title follows semantic commit guidelines
• PR release notes describe the change in a way relevant to app developers, and are capitalized, punctuated, and past tense.
• This is NOT A BREAKING CHANGE. Breaking changes may not be merged to master until 11-x-y is branched.

Release Notes

Notes: Added app.createThumbnailFromPath() API that returns a preview image of a file given its file path and a maximum thumbnail size.

[zcbenz]

This API does not belong to app module, I believe it should be part of shell or nativeImage module (I prefer shell a bit).

/cc @electron/wg-api for more inputs.

[MarshallOfSound]

I think it fits with nativeImage nicely (create from x). I think it was originally put in app because of app.getFileIcon which is kinda weird to be in app as well 🤷

[trop]

@georgexu99 has manually backported this PR to "10-x-y", please check out #25072

[jkleinsc]

The @electron/wg-api approved this via Slack on Aug 20th, 2020

[release-clerk]

Release Notes Persisted

Added app.createThumbnailFromPath() API that returns a preview image of a file given its file path and a maximum thumbnail size.

[gaodeng]

I tried to get app icon and got an error

Error: unable to retrieve thumbnail preview image for the given path

Does this API only get thumbnails of images?
In that case, there doesn't seem to be much difference between this api and nativeImage.createFromPath(path) + resize

[MentalGear]

@gaodeng I'm also trying to get app icons in a cross-platform, high-res way. Could you share whether nativeImage.createThumbnailFromPath worked out for you, or what your best approach was?

[fanchenio]

@MentalGear Facts have proved that high-definition icons can only be obtained through native mode, and electron does not support it.