feat: 增加小程序虚拟支付签名、用户签名方法

[yansongda]

close: #910

[netlify[bot]]

✅ Deploy Preview for pay-yansongda canceled.

Name	Link
🔨 Latest commit	cb49daf37b73153b012a98be0afaddd1e597fa86
🔍 Latest deploy log	https://app.netlify.com/sites/pay-yansongda/deploys/659ff3d7f46c0d0007020014

[codecov[bot]]

Codecov Report

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

Comparison is base (4a1788a) 96.78% compared to head (cb49daf) 96.78%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #924 +/- ## ========================================= Coverage 96.78% 96.78% Complexity 858 858 ========================================= Files 326 326 Lines 5942 5946 +4 ========================================= + Hits 5751 5755 +4 Misses 191 191 ```

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