Update rust/threshold-schnorr/README.md

Author: jessiemongeon1

rust/threshold-schnorr/README.md

@@ -108,6 +108,10 @@ There are four options that are planed to be supported:
 * `test_key_1`: a master **test** key ID that is used in mainnet.
 * `key_1`: a master **production** key ID that is used in mainnet.
 
+For example, the default code in `src/schnorr_example_rust/src/lib.rs` derives
+the key ID as follows and can be deployed locally:
+`SchnorrKeyIds::TestKeyLocalDevelopment.to_key_id(algorithm)`
+
 IMPORTANT: To deploy to IC mainnet, one needs to replace `"dfx_test_key"` with
 either "test_key_1"` or `"key_1"` depending on the desired intent. Both uses of
 key ID in `src/schnorr_example_rust/src/main.mo` must be consistent.