chore: Initialize ADR scaffold

[kakkoyun]

We decided to give it a try https://docs.google.com/document/d/1XkVahJfhf482d3WVHsvUUDaGzHc8TO3sqQlSS80mpGY/edit?tab=t.0#bookmark=id.pru0gqyoqcw9

Implement an ADR system using the templates and the tooling using the official documentation https://adr.github.io

Folder structure:

...
_docs/adr
...

We can use https://github.com/open-telemetry/opentelemetry-go-compile-instrumentation/blob/main/_docs/api-design-and-project-structure.md as the initial ADR.