Add Content Pages

It would be nice to include some additional content, hero images, slogans, and features, both for users to see and web search engines to crawl. Something like https://translate.google.com/about/

• About page - Links to mobile app install. slogans, and features #34

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• Languages - What features and pairing do we offer each language (and maybe dialects?)
  • e.g. English, French, German, etc can pair with multiple signed languages
  • Features like SignWriting dictionary (and size), video dictionary (STS, and size), text input, speech input (optional) for some spoken languages, live camera transcription, take videos for signed languages. offline deep learning models. language detection

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• Contribute - direct people to the sign-writing annotator. Make it into a general sign language collection tool

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• Tools - direct people to this repository. Make it clear that it is all free, everything can be used. Expose some translation APIs for server-side usage.