Link the JavaScript guide to the JSR-generated docs

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Iroha JavaScript is now public here - https://jsr.io/@iroha

It is published alongside with its documentation, generated right from the code. It also contains examples, which also work as doc tests and are actually checked and executed by Deno. JSR is a very convenient place to put the SDK documentation on.

I would advocate for removing the JavaScript guide entirely from the documentation and instead extend the documentation on JSR with SDK-specific details and more examples.