fix: include README.md in Docker build context

The #![doc = include_str!("../README.md")] directive in src/main.rs
requires README.md at compile time. The .dockerignore excluded all
*.md files, causing the Docker build to fail.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: mikkeldamsgaard

.dockerignore

@@ -2,6 +2,7 @@ target/
 .git/
 bin/
 *.md
+!README.md
 docs/
 examples/
 charts/