Add svg test for suggestion rendering

Author: estebank

tests/ui/suggestions/suggestion-highlights.rs

@@ -0,0 +1,14 @@
+//@ only-linux
+//@ compile-flags: --error-format=human --color=always
+
+enum Enum {
+    Foo,
+    Bar,
+}
+impl Enum {
+    fn baz() {}
+}
+
+fn main() {
+    Enum::bar();
+}