ENH: Adapt target viewcode to tango highlighting style

[12rambau]

• add the viewcode extention in the demo site
• use variables for the coloring

Fix #634

[choldgraf]

is there a place in our docs where we can see this in action? It is hard to understand the effects of this without that :-)

Also - it would be useful if we created a section for Sphinx extensions in our colors module, and put all extension-specific CSS rules underneath that section. So similar to how we have sections like:

  /*****************************************************************************
  * layout
  */

We could also have a section like:

  /*****************************************************************************
  * Extensions
  */

[12rambau]

is there a place in our docs where we can see this in action? It is hard to understand the effects of this without that :-)

That's the main purpose of the second commit, result is here: https://pydata-sphinx-theme--635.org.readthedocs.build/en/635/_modules/pandas/core/frame.html#DataFrame.drop

[12rambau]

Also - it would be useful if we created a section for Sphinx extensions in our colors module, and put all extension-specific CSS rules underneath that section. So similar to how we have sections like

Can we keep this one as a comment and see when I'll deal with #623 ?

[choldgraf]

Makes sense to me - this looks good to go IMO, I tried it on dark mode and it looks nice :-)