Ability to pass "--protocol http2" to cloudflared

[lephuongbg]

Describe the feature

The default quic protocol that cloudflared uses doesn't work reliably.

As a workaround, we usually pass --protocol http2 to cloudflared to instruct it to use http2 for tunneling instead.

Would be great if we can do the same thing with untun CLI. It's a great wrapper and simplify thing a lot comparing to using cloudflared manually.

Additional information

• [ ] Would you be willing to help implement this feature?

[TheAlexLichter]

Let's track in #48 to support any kind of extra args

[pi0]

(reopening because while a generic 1-1 mapping might make sense as a feature, untun is still an abstraction helper. not essentially wrapper to cloudflare workers in the future)

[TheAlexLichter]

@pi0 wanna close #48 then instead or allow both?

[pi0]

both are valid imo :) -- like any other unjs layer, we prefer and provide abstraction (this issue) + full control (other issue) over lower layer for advanced/fine-gained custom needs abstraction might not cover.