Setup docs with Vuepress + typedoc

[kaustavdm]

All things docs.

Relevant directories:

• ./docs/ — All markdown files under this directory are used to generate docs
• ./docs/public/ — Any file present here is copied by vuepress to the root of the destination directory
• ./docs/public/api/ — Output directory for typedoc
• ./docs/dist/ — Destination directory for Vuepress, when running npm run build:docs

Relevant commands:

• npm run docs:dev — Run local dev server for vuepress docs
• npm run build:docs — Builds typedoc and then vuepress, with vuepress taking typedoc output

Fixes #46.