feat: add rust import support

.grit/patterns/rust/rust_imports.md

@@ -0,0 +1,58 @@
+---
+title: Rust import management
+tags: [docs, full-examples]
+---
+
+Grit includes a standard `add_import` pattern for adding imports to Rust files.
+
+## `add_import($module, $identifier)` pattern
+
+The `add_import` pattern is used to add a `use` declaration to the top of a Rust file.
+
+```grit
+language rust
+
+`$body` where {
+  add_import(source="std", name="collections::HashMap")
+}
+```
+
+This pattern will add the import to the top of the file, if it is not already present. For example:
+
+Before:
+
+```rust
+fn main() {
+    let map = HashMap::new();
+}
+```
+
+After:
+
+```rust
+use std::collections::HashMap;
+
+fn main() {
+    let map = HashMap::new();
+}
+```
+
+If other imports are present from the same module, they will be added in the same declaration.
+
+```rust
+use std::collections::{HashSet};
+
+
+fn main() {
+    let map = HashMap::new();
+}
+```
+
+```rust
+use std::collections::{HashSet, HashMap};
+
+
+fn main() {
+    let map = HashMap::new();
+}
+```