(implemented, locked) Javascript paramater import

[OAGr]

(Low-priority)

GraphQL can accept some javascript variables. This helps mean that you don't need to use string interpolation, which can be prone to errors.

This way, in Typescript, you could do things like write,

let squiggleString = `normal($mean, $stdev)`
let squiggleResult = squiggle.run(squiggleString, {mean: 3, stdev:10}

let squiggleString2 = `mixture($inputs)`
let squiggleResult2 = squiggle.run(squiggleString2, {inputs: [3,4,5,5,3,2,2,3,3,4,5]}

[OAGr]

Closed with #437