[pygeoapi] committer rights for Gregory Petrochenkov

[Tom Kralidis]

pygeoapi PSC:

I'd like to propose Gregory Petrochenkov [1] as a committer to the
project given his
impressive contributions on the recently added xarray coverage
provider [2], which
will be a popular provider for multidimensional coverage support in the project.

I'll start with my +1.

..Tom

[1] https://github.com/gpetrochenkov-usgs
[2] https://github.com/geopython/pygeoapi/blob/master/pygeoapi/provider/xarray_.py