Add ADOPTERS.md

[oleg-nenashev]

There are many open source projects using Release Drafter. It would be nice to have a page listing open source adoptions that can be used as examples and configuration sources

Examples:

• Jenkins, Global configuration - https://github.com/jenkinsci/.github/blob/master/.github/release-drafter.yml
• Testcontainers, Local configurations for projects, e.g. https://github.com/testcontainers/testcontainers-java/blob/main/.github/release-drafter.yml
• WireMock, Global Configuration - https://github.com/wiremock/.github/blob/main/.github/release-drafter.yml

[jetersen]

Great idea! A quick code search reveals over 7.8k files

I would welcome a PR 👍