Add support for indexmap v2

schemars/tests/indexmap2.rs

@@ -0,0 +1,16 @@
+mod util;
+use indexmap2::{IndexMap, IndexSet};
+use schemars::JsonSchema;
+use util::*;
+
+#[allow(dead_code)]
+#[derive(JsonSchema)]
+struct IndexMapTypes {
+    map: IndexMap<i32, bool>,
+    set: IndexSet<isize>,
+}
+
+#[test]
+fn indexmap_types() -> TestResult {
+    test_default_generated_schema::<IndexMapTypes>("indexmap")
+}