Carbon intensity of different electricity sources

[samtygier-stfc]

Describe the bug

In the Carbon Awareness chapter there are 2 references to wind/renewables having a carbon intensity of 0 gCO2eq/kWh. This is an over simplification.

"If your computer is plugged directly into a wind farm, its electricity would have a carbon intensity of 0 gCO2eq/kWh since a wind farm emits no carbon to produce that electricity."

I think it would be good to show a table or graph of the lifecycle carbon intensities for a range of energy sources. For example the median values from https://www.ipcc.ch/site/assets/uploads/2018/02/ipcc_wg3_ar5_annex-iii.pdf#page=7

I think the would also help make the case that software needs to be efficient even if it is powered by green electricity sources.

I'd be happy to make a pull request.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://learn.greensoftware.foundation/carbon-awareness
2. See the Carbon intensity and Marginal carbon intensity sections

Expected behavior
A bit more detail

[greenhsu123]

Thank you for reaching out and describing how the course could be improved with more detail. The course is only getting updated if it's a simple typo. We will make a note of it and come back to this during the next iteration! Thanks again!