Generating last image of a Composition #1283

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I was playing with the CLI and still action to generate image. Awesome feature 🎉

I wanted to generate the last frame of my Composition and found no other solution than to pass the correct number to the command.

Use Case

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 remotion still src/index.tsx Example --frame -1

Possible Solution

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💡 Negative values of frame could be useful to generate frame relative to the last one. I could take this subject as a contribution.

Hacktoberfest Acceptance Criteria

(edit by @JonnyBurger)

• Take negative integers in renderStill(), renderStillOnLambda(), npx remotion still and npx remotion lambda still and treat them as frames from the back: -1 means last frame, -2 means second to last frame etc.
• Keep up the strict validation, e.g. -200 should not be possible if the duration is only 100 frames.
• Document the feature in the documentation pages of the APIs and commands that accept this option.