Allows the interface to be used as an Identifier for flow plugin (#12254)

packages/babel-parser/test/fixtures/flow/interfaces-as-identifier/class-declaration/input.js

@@ -0,0 +1 @@
+class interface {}

packages/babel-parser/test/fixtures/flow/interfaces-as-identifier/class-declaration/output.json

@@ -0,0 +1,31 @@
+{
+  "type": "File",
+  "start":0,"end":18,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":18}},
+  "errors": [
+    "SyntaxError: Unexpected reserved word 'interface' (1:6)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":18,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":18}},
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start":0,"end":18,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":18}},
+        "id": {
+          "type": "Identifier",
+          "start":6,"end":15,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":15},"identifierName":"interface"},
+          "name": "interface"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start":16,"end":18,"loc":{"start":{"line":1,"column":16},"end":{"line":1,"column":18}},
+          "body": []
+        }
+      }
+    ],
+    "directives": []
+  }
+}