test: integration tests for imports

extension/examples/valid/imports/basic.wacc

@@ -0,0 +1,20 @@
+# import sum from ../sum.wacc
+
+# Output:
+# -33
+
+# Exit:
+# 0
+
+# Program:
+
+import "../sum.wacc" (sum)
+
+begin
+  int main() is 
+    int result = call sum(-10, -23) ;
+    return result
+  end
+  int result = call main() ;
+  println result
+end