Add 95th and 99th percentile to aggregation

[artiya4u]

The 95th and 99th percentile are crucial for some applications e.g. network latency visualization.
I proposed new aggregation operations p95 and p99 to calculate the 95th, and 99th percentile respectively.
By using the well-defined quantiles() function, used by q1 and q3 operations.
I modify it to add the p95 and p99 without making a new function.

[domoritz]

Related issue: vega/vega-lite#4439

Can I propose to add a parameter to set the quantile and to have an ntile aggregate instead?

Note that Vega already has a quartile transform: https://vega.github.io/vega/docs/transforms/quantile/.

[artiya4u]

@domoritz

vega/vega-lite#4439

I came from the issue, I just think my proposed p95, p99 operations are just faster to implement and straightforward to use for an average user. It cover most of my use cases(network latency, benchmark result). I would love my solution to share with everyone who has the same problem. The Ntiles with parameter solution might be too hard for me since no one wants to work on it for a year.

[domoritz]

Fair points. Please remove the compiled files and also update the ts types so @jheer can do a review.

[artiya4u]

OK, I think it is ready to review.

[jkillian]

Was just looking for this feature today 😄 I think it might be nice to throw p90 in this PR as well if there's no reason not to - p50, p75, p90, p95, and p99 are a common set of performance-related percentiles I've often seen.