Migrate to typescript

[lovasoa]

Hello, Feel free to close this PR if you are not interested. This is a work-in-progress port to typescript.

[piotrblasiak]

@erdtman Do you have any interest in this? @lovasoa has done a great job and I am conflicted as what library to choose as clearly a lot of work has been put into this one, and @lovasoa has made a great fork as well. Feels like a waste of effort to have 2 well maintained libraries...

[iamgabrielsoft]

This is brillant from @lovasoa, wonderful work done here

[lovasoa]

Thank you. I published my fork on npm under the name "cosette". In addition to the type annotations, it fixes bugs, is fully isomorphic (works on node.js and the web), uses the fast and lightweight web crypto APIs when available, and supports more encryption and signature algorithms.