mark feature allowing user to permanently highlight data in chart

[joshhjacobson]

Slickgrid example to follow.

[BigFatDog]

Thank you so much for your time and efforts on this pull request。

[joshhjacobson]

Happy to do it, thanks for walking me through it!

[BigFatDog]

@joshhjacobson I just found that demo page is not working. I believe source code is good. There are just some minor issues with the demo.html itself.

1. reference path. demo directory and dist directory are in the same level in rollup dev server. It will work when running npm run dev

   <script src="../dist/parcoords.standalone.js"></script>
   ...
   <link rel="stylesheet" type="text/css" href="../dist/parcoords.css">
   should be:
   <script src="./parcoords.standalone.js"></script>
   <link rel="stylesheet" type="text/css" href="./parcoords.css">

2. css style:

   <div id="plot" class="parcoords" style="height:200px; width=100%;"></div>
   // width: 100%

3. slick grid doesn't show data when brushed. (I remember the demo usage is to brush parcoords, see brushed data in grid and then check a row in slick grid so as to mark it on parcoords)

4. please link demo.html to index.html

Would you please make a pull request to fix demo.html? If you're busy, just tell me and let me do this.

[joshhjacobson]

Good catch, I'll fix this either today or early next week and submit a pull request.

[BigFatDog]

Happy to do it, thanks for walking me through it! It has been my pleasure.