[WIP]: Add quantile shortcut
 - [x] closes #15023 
 - [ ] tests added / passed
 - [ ] passes ``git diff upstream/master | flake8 --diff``
 - [ ] whatsnew entry

tests! ## [Current coverage](https://codecov.io/gh/pandas-dev/pandas/pull/15032?src=pr) is 84.76% (diff: 33.33%)
> Merging [#15032](https://codecov.io/gh/pandas-dev/pandas/pull/15032?src=pr) into [master](https://codecov.io/gh/pandas-dev/pandas/branch/master?src=pr) will decrease coverage by **<.01%**

```diff
@@             master     #15032   diff @@
==========================================
  Files           145        145          
  Lines         51131      51138     +7   
  Methods           0          0          
  Messages          0          0          
  Branches          0          0          
==========================================
+ Hits          43346      43347     +1   
- Misses         7785       7791     +6   
  Partials          0          0          
```

> Powered by [Codecov](https://codecov.io?src=pr). Last update [6141754...a3b713b](https://codecov.io/gh/pandas-dev/pandas/compare/6141754e3ef0574fda35a49925aa629655fd16a0...a3b713beffd1d78b7a3b80c3275410654cce30ca?src=pr) can you rebase / update if you'd like to add tests and finish this up, pls ping. Ping @srinivasreddy. Would have used this :)