Option for getting output of specific frames

[affankhan43]

Just need to use to options for rendering specific frame images

• @param {object} [opts.startFrame] - Optional lottie-web initialSegment set segment for exporting specific frame
• @param {object} [opts.endFrame] - Optional lottie-web initialSegment set segment for exporting specific frame

[amiantos]

Suggested change

	startFrame = 1000000,
	endFrame = 1000000,

[amiantos]

How would you use this to get a single frame of animation? I'm confused by the -1 you're doing to the endFrame value. If you want frame 0 of the animation, how would you get it in this context? startFrame = 0, endFrame = 1? I dunno if that makes sense to me.

Can you add some tests? Full disclosure, I tried out this solution on my own and it didn't appear to work.