Export encodeTransaction method in near-api-js package

[gtsonevv]

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• [ ] If this is a code change: I have written unit tests.
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• [ ] If this is a new API or substantial change: the PR has an accompanying issue (closes #0000) and the maintainers have approved on my working plan.

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[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: e90e648ca4d6c3505141ad2ec666bbd9375b1289

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

| Name | Type | | ----------------- | ----- | | near-api-js | Patch | | @near-js/cookbook | Patch |

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