docs: update installation guide

[ColinEberhardt]

It looks like you need to load perspective.js in order to instantiate the 'engine':

const worker = perspective.worker();

[texodus]

Thanks for the PR! Much appreciated.

To clarify, perspective.js is the API for the WebWorker. This is already a dependency of perspective.view.js, but this bundle does not expose it as a global variable; rather, it will internally create it's own WebWorker as needed to manage any data passed to it, which you can access via the <perspective-viewer>'s worker property like so

let elem = document.getElementById('my_viewer');
let table = elem.worker.table([{x:1, y:2}]);
elem.load(table);

Thus, perspective.js is only needed if you A) want to create additional WebWorkers or B) just want to use the Perspective engine library directly. We could alternatively just export the perspective symbol globally from perspective.view.js - feedback welcome here. Either way, this part of the documentation needs some substantial fleshing out!

[ColinEberhardt]

Thanks for merging the PR.

Either way, this part of the documentation needs some substantial fleshing out!

Your API documentation is really quite good. What you are lacking is any 'getting started' type of documentation. These are typically much more tutorial-based.

For our d3fc library we have a simple step-by-step guide here:

https://d3fc.io/introduction/building-a-chart.html

And a more advanced version as a blog post:

https://blog.scottlogic.com/2018/09/21/d3-financial-chart.html