JWK Implementation for import/export

[olegbespalov]

What?

This is an implementation of the JWK export/import.

I've decided to use the popular library instead of self-tailored since, for the following algorithms, the JWK could be more complicated in terms of maintaining standards.

How did I test it?

• I did rely on the existing Web Platform tests (uncommented cases).
• also I've checked that the generated in nodejs key could be imported by the xk6-webcrypto

Related PRs:

This PR is based on #62

Why?

JWK is part of the specification.

Closes: #37

[oleiade]

Before I forget, we should also update the README tables to match the newly introduced support for JWK in import and export operations. At least for the sake of future selves 😸

[olegbespalov]

@oleiade, the readme tables have no JWK (formats) dimension, but you are correct that it's worth mentioning the current state. I've made a note in ea6ac87