bump version to 2.0.0

bump version to 1.9.0

modify changelog

bump version to 1.6.2

1. add one param(gasUniPrice) in utils.tx.generateRawUserTransaction …

…2.add encoding.stringToBytes && encoding.bytesToString

fix typo

bump version to 1.4.0

fix typo

Merge branch 'vote'

Move test cases for decoding event data and key to 'src/onchain_event…

…s/index.spec.ts'