Feature request: Filmstrip export as single image

[JCofman]

Hi,

first of all thank you for this awesome library. I would really like to extract a single filmstrip image as it is possible on the WPT compare page. Since I run webpagetest on a CI pipeline and want to post the results to the commit as seen here -> inovex/blazinglyfast@b799343 . Currently I have to concatenate the array of images to a markdown formatted table.

Maybe this is already possible kinda similiar to $ webpagetest video [testids] but I was not able to find the correct api. 🙈