[blog] opentelemetry-injector announcement

[svrnm]

Related SIG issue: open-telemetry/opentelemetry-injector#11
Donation proposal: open-telemetry/community#2580

With the injector donation accpeted we want to have a blog post announcing this new subproject and inviting contributions and users to take a look.

@isabella-rose-l and I will help @open-telemetry/injector-maintainers to write the blog post.

[atoulme]

This is now live: https://opentelemetry.io/blog/2025/otel-injector/