WIPO Global Innovation Index - GitHub measure

For the first time, developers' contributions to innovation on GitHub are included in the World Intellectual Property Organization's [Global Innovation Index](https://www.wipo.int/global_innovation_index/en/). The measure is defined as
> GitHub commit pushes received (per million population, 15–69 years old) | 2021

Opening this issue for reactions and feedback on our measure. We will consider these community inputs ahead of next year's report.

No source files, tests, or implementation entry points are named. Start by reviewing the issue text and the linked WIPO Global Innovation Index definition; the work is not complete until the requested community feedback or a specific documentation change is defined.

索引モデルが issue の本文から書いたものです。