Please add js-conflux-sdk version

[Thegaram]

What problem are you trying to solve?

Please show js-conflux-sdk version on GitHub and docs for each release. This makes it much easier to find the relevant docs for the injected API.

Describe the solution you'd like

Maybe the best solution is to add this right under the title in README.md:

(with better styling of course)

In addition to this, it could also be added to the release notes (when updated) and the docs.

Additional context

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