Prep to release v0.42.0 (#2003)

* Prep to release v0.42.0

* Remove test_context reference from example

* standalone_crate for doc tests because codegen is expensive

* fmt

codegen/src/api/mod.rs

@@ -410,19 +410,24 @@ pub struct StructFromVariant {
 /// Returns the TokenStream of the type alias module.
 ///
 /// E.g a struct like this:
-/// ```ignore
+///
+/// ```rust,ignore
 /// pub struct SetMaxCodeSize {
 ///     pub new: ::core::primitive::u32,
 /// }
 /// ```
+///
 /// will be made into this:
-/// ```ignore
+///
+/// ```rust,ignore
 /// pub struct SetMaxCodeSize {
 ///     pub new: set_max_code_size::New,
 /// }
 /// ```
+///
 /// And the type alias module will look like this:
-/// ```ignore
+///
+/// ```rust,ignore
 /// pub mod set_max_code_size {
 ///     use super::runtime_types;
 ///     pub type New = ::core::primitive::u32;