added issue template, same as the one in keripy

[codecov[bot]]

Codecov Report

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

Project coverage is 93.74%. Comparing base (18d3ad7) to head (6d49c77). Report is 31 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #317 +/- ## ========================================== + Coverage 93.06% 93.74% +0.68% ========================================== Files 36 36 Lines 7121 7979 +858 ========================================== + Hits 6627 7480 +853 - Misses 494 499 +5 ```

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