sip.create() does not export function "makeResponse"
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# Bug Report

### Describe the Bug
The function call to `sip.create()` (kirm sip.js module) does not return the function `makeResponse`.
If the SIP peer sends a BYE during the SIP session, this will lead to the following error message.
The SIP stack catches this exception and produces a 500 SIP response code.
```
TypeError: this.sipClient.makeResponse is not a function
    at sip-call.js:91:52
```

See the return statement here: 
https://github.com/dgreif/ring/blob/8ef25acca66c533873b7fd43c7c899e34b4a7617/api/sip.js#L1498

Only these functions are exported:
-   `send `
-   `stop `
-   `encodeFlowUri `
-   `decodeFlowUri `
-   `isFlowUri`
-  `hostname `

However, this interface defined here assumes that `makeResponse` is exported:
https://github.com/dgreif/ring/blob/8ef25acca66c533873b7fd43c7c899e34b4a7617/api/sip-call.ts#L47-L58

### Environment
 - OS: Ubuntu 20.04
 - Node.js: 16.13.1
 - NPM: 8.1.2
 - ring-client-api: master
