Twirp suport

[ishumilova]

Todo:

• Protobuf endpoints support
• JSON endpoints support
• Tests

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[mstoykov]

Hi, @ishumilova I see that you are still working on this PR, but I just wanted to note that we are unlikely to add support for this to k6.

Many people have wanted support for different protocols over the years and we likely will add a lot more to the core of k6, but the current proposed solution for people who want to use k6 and are willing to write the code is to make an extension. This lets you do your work and use k6 but doesn't require us to review your code and you to make it compliant with our requirements or to be building functionality that we want in k6 :).

There is some small amount of documentation (that as mentioned there can get outdated) that can help you but in reality, it's the same as having to develop it for the core k6 it just lives in its own repo and gets build with xk6.

Sorry for the inconvenience, good luck and I will be glad to see your extension in the list of extensions.