feat: Show category counts/percentages on ValueCounts hover

[jwilber]

Great project idea!

This PR adds in some UX seen in the Observable Summary Table, where hovering over values in the ValueCountsPlot displays the corresponding row count/percentage (see demo of PR in action in video below).

Observable Example:

quakPRObservable.mov

Quak Example (this PR):

quakPRHoverRowCount.mov

Two small differences here versus Observable:

1. I format the percentage via d3.format(".1%"), while they appear to use d3.format(".0%"). (A future improvement could use a ternary to check if the percentage is less than 1, if so, format via d3.format(".1%") or .2,, otherwise, d3.format(".0%").

2. On mouseout, they appear to show the JS data-type, while I show the type provided by the arrow.Field (as that's what was displayed by default in quak).

Note:

• This PR also brings in some linting/formatting changes, which occurred after running deno lint + deno fmt.
• This PR only affects the Value Counts plots (for categorical data). I can happily add another PR for the histogram as well 😄

[manzt]

Love it! Thanks for the contribution. I'll give a review tomorrow.

re: deno fmt... not sure what's going on there. My guess is that you may have some editor "format on save" setting, which likely uses prettier (creating new line indentation, etc) and and then the deno fmt formats that new-line delimited code with dprint.

[jwilber]

sgtm! I just went ahead and reset the committed linting changes.

[manzt]

Looks great! Stellar PR. Thanks again for the contribution.