Add link to a npmjs wasm module

[olpa]

Let me add a link to the npmjs module with bindings for jsonnet. There is already one, but the new module is based on the Golang version and provides "libjsonnet.wasm", which otherwise has to be downloaded from a helper dir on jsonnet's site.

[google-cla]

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[olpa]

CLA is signed.

[johnbartholomew]

Thanks for the contribution, and sorry for the delay in processing it!