Declare esprima as dependency in package.json

[troglotit]

When I use vue-styleguidist to create a client-side npm-project when I declare styleguidist as a dependency, and because of esprima package is not specified explicitly in package.json - it gets resolved differently. I did see 2.7.3 and 4.0.0 versions in both of my yarn and npm lockfiles, but yarn resolves to 2.7.3 while npm to 4.0.0 in first-level node_modules folder. And Esprima at 2.7.3 used UMD, and for that, syntax like

import esprima from 'esprima'
esprima.parse() // -- is ok

But for 4.0.0 Esprima migrated to Typescript (I think they migrated in 3.0.0 version), and it uses ES modules. And for that, former usage of module would break (because of how named exports).

import { parse } from 'esprima'
parse() // -- this would work

I tried to verify if it works, but because of #15 I couldn't verify it 😅.

Hope everything's clear, feel free to ask anything or edit PR!

[rafaesc]

Thanks for the contribution!

I'll update the package on the weekend