Build and maintain an overview of related tools

[Grim-bot]

Description of the issue:

• We should build an overview (e.g., annotated list) of existing tools for carbon footprint measurement and update it periodically.
• This is necessary to make good strategic decisions about whose needs (and which needs) we want to meet, and how best to meet them.
  • For instance, given the current size of the project, it might be useful to merge a different open-source project into this repo, combine, and build on top.

This list should ideally be linked from the README, unless we create a Wiki to discuss the project's strategy (then, an overview of existing tools would fit more naturally in the Wiki).

Examples to include:

• http://www.codecarbon.io/
  • This one's stated goals / purpose are exactly the same as cumulator, and they already have a website and a better name. Since their project is open-source, we could:
    • propose a collaboration to add the features we need, or, if that fails,
    • fork their repo and build on top of it.
  • Either of these options would probably require less work than starting from the current state of cumulator.
• https://www.websitecarbon.com/