Replace matplotlib seaborn style plots with Arviz Plots in Documentation

[mjhajharia]

While working on #3859 , we saw seaborn-darkgrid is not the best of color friendly styles, and seaborn-colorblind is not regularly updated. arviz-darkgrid is relatively better and additionally as @OriolAbril pointed out - matplotlib styles have not been updated in ~5 years, so using ArviZ would give us better control and the ability to easily update the style if needed.

This PR changes plt.style.use("seaborn-darkgrid") to arviz-darkgrid and adds a line of importing arviz, which is anyway a pymc3 dependency.

These changes are in continuous.py and discrete.py (i.e. The sample plots in documentation)

[OriolAbril]

Looks good, thanks!

[mjhajharia]

@canyon289 feel free to have a look anytime and merge if satisfactory.

[canyon289]

Looks great. As a matter of proceedings I personally dont have to review ever PR here (thankfully)
What usually happens is one core contributor, like Oriol, will approve the changes and then another maintainer will take a quick glance and merge it usually within a couple of days and hopefully wont leave you waiting too long

[mjhajharia]

Understandable, noted.

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On 24 Mar 2021, 9:47 PM +0530, Ravin Kumar ***@***.***>, wrote: Looks great. As a matter of proceedings I personally dont have to review ever PR here (thankfully) What usually happens is one core contributor, like Oriol, will approve the changes and then another maintainer will take a quick glance and merge it usually within a couple of days and hopefully wont leave you waiting too long — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub, or unsubscribe.