Add support for Blenderbot and BlenderbotSmall (Closes #37, #29)

[xenova]

Had a few hours over the weekend, so I decided to knock this issue out. It hasn't been a major priority simply because these models are outdated and there are better alternatives. The hope is that later versions of blenderbot are released (and added to transformers; see here) and this can serve as a starting point for adding support for those.

NOTE Despite having similar names, there are significant differences between the Blenderbot and BlenderbotSmall tokenizers. The current BlenderbotSmallTokenizerFast is broken in the python library, so there are some slightly hacky and non-standard approaches taken to get it working. See Xenova/blenderbot_small-90M for more information.

Example usage:

Blenderbot

let generator = await pipeline('text2text-generation', 'Xenova/blenderbot-400M-distill');
let output = await generator('What is your name?', { num_beams: 1 });
console.log(output)
// [ ' My name is Jessica.' ]

BlenderbotSmall

let generator = await pipeline('text2text-generation', 'Xenova/blenderbot_small-90M');
let output = await generator('What is your name?', { num_beams: 1 });
console.log(output)
// [ 'my name is sam.' ]

[HuggingFaceDocBuilderDev]

The documentation is not available anymore as the PR was closed or merged.