Compile/test ES6/TypeScript/??? action code in jison grammars?

[GerHobbelt]

Sideways related to #14: here the challenge is setting up jison so that its internal code generation, code validation and 'live parser' generation logic can cope (= precompile) sources which are not 'vanilla JS', i.e. which are not JavaScript which is supported out of the box on the platform you're currently running jison on.

[GerHobbelt]

Related: #22

[GerHobbelt]

Note to self: this issue basically says: "whatever you do, also have a workflow choice where nothing is validated/expected to be 'sensible' JavaScript action code for whatever definition of 'sensible': just copy everything as-is as let the user play entirely their own game. Less precise error discovery and reporting but arbitrary input = arbitrary output, no hold-up or blocking b0rk along the way."

[GerHobbelt]

Related: #46