feat: mp-baidu payment

src/platforms/mp-baidu/service/api/index.js

+export function requestPayment (params) {
+  let parseError = false
+  if (typeof params.orderInfo === 'string') {
+    try {
+      params.orderInfo = JSON.parse(params.orderInfo)
+    } catch (e) {
+      parseError = true
+    }
+  }
+  if (parseError) {
+    params.fail({
+      errMsg: 'requestPayment:fail: 参数 orderInfo 数据结构不正确，参考：https://uniapp.dcloud.io/api/plugins/payment?id=orderinfo'
+    })
+  } else {
+    swan.requestPolymerPayment(params)
+  }
+}