ENH: Added 2 blogs related to nx-parallel and NetworkX

[Schefflera-Arboricola]

• The main subject relates to at least one project affiliated to the Scientific Python Ecosystem.
• I have the right to publish the content under BSD 3-Clause License for the code and Creative Common CC-BY-4.0 License for the text.
• Images have been compressed using a tool like pngquant.

[jarrodmillman]

Thanks!! It looks like we will need a new theme release before merging this (I will take care of that soon).

I also will add a figure shortcode to complement the image shortcode:

• https://theme.scientific-python.org/shortcodes/#image

I had one already, but need to review something before going forward.

I will review this PR soon and provide comments/suggestions.