support transaction encode/decode

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (6b3a9f1) 43.24% compared to head (36724f6) 43.24%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## release-v3.0.0 #254 +/- ## =============================================== Coverage 43.24% 43.24% =============================================== Files 5 5 Lines 666 666 =============================================== Hits 288 288 Misses 307 307 Partials 71 71 ```

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