Version of EOSJS
"eosjs": "^20.0.0-beta3",

Describe the bug
when using eosJS to send a transaction in common JS. Following the documentation provides this error.

const signatureProvider = new JsSignatureProvider(privateKeys);
                          ^

TypeError: JsSignatureProvider is not a constructor
    at Object.<anonymous> (/Users/jesse/Desktop/blockx/eosTest/sendTransaction.js:7:27)
    at Module._compile (module.js:652:30)
    at Object.Module._extensions..js (module.js:663:10)
    at Module.load (module.js:565:32)
    at tryModuleLoad (module.js:505:12)
    at Function.Module._load (module.js:497:3)
    at Function.Module.runMain (module.js:693:10)
    at startup (bootstrap_node.js:191:16)
    at bootstrap_node.js:612:3

when console logging JsSignatureProvider you get

{ default: [Function: JsSignatureProvider] }

To Reproduce
follow your documentation for sending a transaction with commonJS.

Expected behavior
Receive a transaction hash

Desktop (please complete the following information):

• macOS high Sierra

Additional context
I have solved this problem in 2 ways. One was by importing as .default. This would require a documentation change. However, this issue is only seen in typescript when exporting default and not when using module.export. So I have created a PR that makes that change when exporting the JsSignatureProvider.