ABI support

[scholtz]

Is your feature request related to a problem? Please describe. By the best practicies it is better to write teal code which supports ABI calls.

Describe the solution you'd like Please implement ABI support to tealish.

Describe alternatives you've considered All other pyteal compilers support abi. Pyteal, beaker, ...

Additional context I like idea of tealish that you copy the comments to the teal or that you use the same opcode names as in teal, but it is quite crucial for new projects to use the abi. Soon there will be release of shared resources and this will drive adoption of single abi calls which might be more complex.