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

cli/src/commands/diff.rs

@@ -18,7 +18,7 @@ use subxt_metadata::{
 /// Explore the differences between two nodes
 ///
 /// # Example
-/// ```
+/// ```text
 /// subxt diff ./artifacts/polkadot_metadata_small.scale ./artifacts/polkadot_metadata_tiny.scale
 /// subxt diff ./artifacts/polkadot_metadata_small.scale wss://rpc.polkadot.io:443
 /// ```

cli/src/commands/explore/mod.rs

@@ -20,6 +20,7 @@ mod runtime_apis;
 /// # Example
 ///
 /// Show the pallets and runtime apis that are available:
+///
 /// ```text
 /// subxt explore --file=polkadot_metadata.scale
 /// ```

cli/src/commands/explore/runtime_apis/mod.rs

@@ -19,7 +19,7 @@ use subxt_metadata::RuntimeApiMetadata;
 
 /// Runs for a specified runtime API trait.
 /// Cases to consider:
-/// ```txt
+/// ```text
 /// method is:
 ///   None => Show pallet docs + available methods
 ///   Some (invalid) => Show Error + available methods