Add github action to generate "OSS Adopters" page

[popey]

The "OSS Adopters" page is automagically generated based on network information in our git repos. The script scripts/generate-adopters-info.sh was a quick and dirty hack to create the page using the Python tool, github-dependents-info. Some headline adopters come from data/adopters.json and can be curated as desired.

We should automate this using a GitHub action to be executed periodically, so the data on the page is fresh.