doc: add module documentation for gh-workflow

crates/gh-workflow/src/ctx.rs

@@ -1,3 +1,5 @@
+//! A type-safe implementation of workflow context: <https://docs.github.com/en/actions/writing-workflows/choosing-what-your-workflow-does/accessing-contextual-information-about-workflow-runs>
+
 use std::fmt;
 use std::marker::PhantomData;
 use std::rc::Rc;
@@ -6,9 +8,6 @@ use gh_workflow_macros::Context;
 
 use crate::Expression;
 
-///
-/// A type-safe implementation of GitHub Actions context expressions.
-/// Implemented based on the documentation provided here: <https://docs.github.com/en/actions/writing-workflows/choosing-what-your-workflow-does/accessing-contextual-information-about-workflow-runs>
 #[derive(Clone)]
 pub struct Context<A> {
     marker: PhantomData<A>,

crates/gh-workflow/src/error.rs

@@ -1,3 +1,6 @@
+//! This module defines the `Error` enum and the `Result` type alias used
+//! throughout the crate.
+
 #[derive(Debug, derive_more::From)]
 pub enum Error {
     IO(std::io::Error),

crates/gh-workflow/src/generate.rs

@@ -1,3 +1,6 @@
+//! This module provides functionality to customize generation of the GitHub
+//! Actions workflow files.
+
 use std::io::ErrorKind;
 use std::path::PathBuf;
 use std::process::Command;

crates/gh-workflow/src/release_plz.rs

@@ -1,3 +1,5 @@
+//! A typed representation of the `release-plz` action in a GitHub workflow.
+//! Docs: <https://github.com/release-plz/action>
 use derive_setters::Setters;
 
 use crate::{Step, Use};

crates/gh-workflow/src/toolchain.rs

@@ -1,4 +1,5 @@
-//! The typed version of https://github.com/actions-rust-lang/setup-rust-toolchain
+//! The typed version of the `setup-rust-toolchain` action in a GitHub workflow.
+//! Docs: <https://github.com/actions-rust-lang/setup-rust-toolchain>
 
 use std::fmt::{Display, Formatter};