Litho: Migrate Website to Docusaurus 2 Alpha

[Drewbi]

@yangshun mentioned Litho was interested in porting the documentation website over to Docusaurus V2.

@teikjun and I are working on moving everything over currently and we will be making a PR soon.

I anticipate some alterations to the deployment config will have to be made as I'm not too experienced in that field.

[yangshun]

Relevant issue - https://github.com/facebook/docusaurus/issues/1834

[colriot]

Finally all your work was deployed publicly and ready to be used with https://github.com/facebook/litho/commit/8934eefb6900487d6336b74009007476d5c11ab1!

Thanks again for helping us with that, @Drewbi @teikjun !

[Drewbi]

Ayy thanks for the merge, hope you like the new framework :)