Add a .decorrelationrc file for general configuration

[kanglcn]

i.e., Available GPU, GPU number, available thread, default plot figsize, dpi, etc.

[kanglcn]

ref: https://stackoverflow.com/questions/7567642/where-to-put-a-configuration-file-in-python

I prefer toml format.

content: CUDA_VISIBLE_DEVICES, by default, all Number of cpu cores, by default, all matplotlib figsize, by default, 10,10

[kanglcn]

[x] And dask dashboard link. Look like dask_cuda do not support it.

[kanglcn]

not needed at all