docs(readme): add per-crate READMEs and enhance wrkflw crate README

crates/github/README.md

@@ -0,0 +1,23 @@
+## wrkflw-github
+
+GitHub integration helpers used by `wrkflw` to list/trigger workflows.
+
+- **List workflows** in `.github/workflows`
+- **Trigger workflow_dispatch** events over the GitHub API
+
+### Example
+
+```rust
+use wrkflw_github::{get_repo_info, trigger_workflow};
+
+# tokio_test::block_on(async {
+let info = get_repo_info()?;
+println!("{}/{} (default branch: {})", info.owner, info.repo, info.default_branch);
+
+// Requires GITHUB_TOKEN in env
+trigger_workflow("ci", Some("main"), None).await?;
+# Ok::<_, Box<dyn std::error::Error>>(())
+# })?;
+```
+
+Notes: set `GITHUB_TOKEN` with the `workflow` scope; only public repos are supported out-of-the-box.