feat: add typescript-axios template

[mnahkies]

• new template typescript-axios based on https://github.com/axios/axios

• compared to the typescript-fetch template it's quite "lossy", eg: you don't retain as much information about possible error responses. as we can't type hint possible exceptions I don't see a way to avoid this (short of catching and returning a result type, but this would seem to defeat the purpose of using axios)

• included a couple of scripts using the github api as a test / sample

• Documentation

• Publish Alpha

Some dog fooding has been done, but not as much as the fetch template yet. Likely to some rough edges that will need to be fixed forward.

Testing
Alpha version published as:

@nahkies/openapi-code-generator@0.1.1-alpha.13
@nahkies/typescript-axios-runtime@0.1.1-alpha.13