chore: add a couple of rust test snippets

site-modules/core/files/vim/snippets/snippets/rust/it.snippet

@@ -0,0 +1,9 @@
+# name: Rust test
+# key: it
+# contributor: Ade Attwood <code@adeattwood.co.uk>
+# filetypes: rust
+# --
+#[test]
+fn $1() {
+  $0
+}

site-modules/core/files/vim/snippets/snippets/rust/test.snippet

@@ -0,0 +1,9 @@
+# name: Test module
+# key: test
+# contributor: Ade Attwood <code@adeattwood.co.uk>
+# filetypes: rust
+# --
+#[cfg(test)]
+mod tests {
+  $0
+}