Make return value never undefined if passing `acceptCloudflareNotice: true`

[chadxz]

Describe the feature

This is a small thing but it would be nice if the startTunnel() return type did not include undefined if I pass acceptCloudflareNotice: true as an option. Looking at the code, the only scenario it would be undefined is if it wasn't accepted.

I'm no TypeScript wizard but it seems like it may be possible?

Additional information

• Would you be willing to help implement this feature?