Custom Granularity does not work with resultset.chartPivot()

[dvalemark]

Describe the bug
When using the new custom granularity option for a query and use the chartPivot() on the resultset it throws the error:
"Error: Unsupported time granularity: sunday_week"

The data returned by the query is correct and the query itself works great with the custom granularity.

To Reproduce
Steps to reproduce the behavior:

1. Create a custom granularity in model
2. Create a query using the custom granularity
3. Use .chartPivot() function on the result
4. See error

Expected behavior
I expected the .chartPivot() to be able to handle the new custom granularity

Screenshots

Version:
0.36.2

Additional context
When looking through your code in cubejs-client-core/src/ResultSet.js line 355 i found a check to ensure granularity was part of the TIME_SERIES variable. The TIME_SERIES variable doesn't seem to support custom granularity, I'm not sure if this was to be included in the release with custom granularity or not but I wanted to raise the issue.