chore: checkpoint before Python removal

vendor/crypto-bigint/tests/const_residue.rs

@@ -0,0 +1,10 @@
+//! Test to ensure that `const_residue!` works from outside this crate.
+
+use crypto_bigint::{const_residue, impl_modulus, modular::constant_mod::ResidueParams, U64};
+
+impl_modulus!(TestMod, U64, "30e4b8f030ab42f3");
+
+fn _test_fun() {
+    let base = U64::from(2u64);
+    let _base_mod = const_residue!(base, TestMod);
+}