Add regression test for #706 and #708

Author: GuillaumeGomez

testing/tests/auxiliary/paths.rs

@@ -0,0 +1 @@
+define_template!();

testing/tests/paths.rs

@@ -0,0 +1,14 @@
+// This test ensures that template paths work even when created from another file.
+#[test]
+fn cross_file_paths() {
+macro_rules! define_template {
+    () => {
+        #[derive(askama::Template)]
+        #[template(path = "base-decl.txt")]
+        struct Empty {}
+    }
+}
+
+#[path = "./auxiliary/paths.rs"]
+mod a;
+}