Add GitHub stars badge to sites

[mmcky]

@jstac mentions the GitHub stars badge on the julia site

https://julialang.org/downloads/

Perhaps we should add them to our lecture series:

• QuantEcon.py
• QuantEcon.jl
• lecture sites

If we don't want to have the count displayed, but want people to be able to watch or star a site we could use

https://buttons.github.io

to generate the code and add it to the themes.

[jstac]

Thanks @mmcky . I don't mind to have the count displayed, even if it's low :-)

[mmcky]

@DrDrij @AakashGfude would there be an easy way to add this to the theme (perhaps on the RHS under the logo and powered by jupyterbook text.

[DrDrij]

Example:

The format would be:

https://badgen.net/github/stars/[org-name]/[repo-name]

eg. <img src="https://badgen.net/github/stars/quantecon/quantecon-book-theme">

(perhaps wrap it in a Paragraph element)
<p><img src="https://badgen.net/github/stars/quantecon/quantecon-book-theme" /></p>