Bring back modified hello_world example as dependencies

Author: mkaput

examples/dependencies/README.md

@@ -0,0 +1,3 @@
+# `dependencies`
+
+This example showcases using external packages, here: [Alexandria](https://github.com/keep-starknet-strange/alexandria).

examples/dependencies/Scarb.toml

@@ -0,0 +1,8 @@
+[package]
+name = "dependencies"
+version = "0.1.0"
+
+# See more keys and their definitions at https://docs.swmansion.com/scarb/docs/reference/manifest.html
+
+[dependencies]
+alexandria_math = { git = "https://github.com/keep-starknet-strange/alexandria.git" }

examples/dependencies/src/lib.cairo

@@ -0,0 +1,16 @@
+use alexandria_math::fibonacci::fib;
+
+fn double_fib(a: felt252, b: felt252, n: felt252) -> felt252 {
+    2 * fib(a, b, n)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::double_fib;
+
+    #[test]
+    #[available_gas(100000)]
+    fn it_works() {
+        assert(double_fib(0, 1, 16) == 1974, 'it works!');
+    }
+}