chore: add docs for contractimport and contractfile macro sha256 verification

Author: mootz12

soroban-sdk/src/lib.rs

@@ -305,6 +305,22 @@ pub use soroban_sdk_macros::contracterror;
 /// `export = false` and do not produce spec entries. See [`_features`] for
 /// details.
 ///
+/// ### SHA-256 Verification
+///
+/// An optional `sha256` parameter can be provided to verify the integrity of
+/// the WASM file at compile time. When provided, The macro computes the 
+/// SHA-256 hash of the WASM file at compile time and produces a compile error 
+/// if it does not match the provided value.
+///
+/// ```ignore
+/// mod contract_a {
+///     soroban_sdk::contractimport!(
+///         file = "contract_a.wasm",
+///         sha256 = "d5bc0a5b4...",
+///     );
+/// }
+/// ```
+///
 /// ### Examples
 ///
 /// ```ignore
@@ -1008,6 +1024,19 @@ pub use soroban_sdk_macros::contractspecfn;
 /// into a constant, and so it is usually unnecessary to use [`contractfile`]
 /// directly, unless you specifically want to only load the contract file
 /// without generating a client for it.
+///
+/// ### SHA-256 Verification
+///
+/// Unlike [`contractimport`], `contractfile` **requires** a `sha256`
+/// parameter. The macro computes the SHA-256 hash of the WASM file at compile
+/// time and produces a compile error if it does not match the provided value.
+///
+/// ```ignore
+/// soroban_sdk::contractfile!(
+///     file = "contract_a.wasm",
+///     sha256 = "d5bc0a5b4...",
+/// );
+/// ```
 pub use soroban_sdk_macros::contractfile;
 
 /// Panic with the given error.