fixed type definition about export the stylesheet serializer (#259)

Author: kotarella1110

package.json

@@ -28,6 +28,7 @@
     "@babel/preset-env": "^7.0.0",
     "@babel/preset-react": "^7.0.0",
     "@testing-library/react": "^8.0.1",
+    "@types/pretty-format": "^20.0.1",
     "babel-core": "^7.0.0-bridge.0",
     "babel-eslint": "^10.0.1",
     "babel-jest": "^24.8.0",

typings/index.d.ts

@@ -1,3 +1,5 @@
+import { Plugin, NewPlugin } from 'pretty-format'
+
 declare namespace jest {
   interface AsymmetricMatcher {
     $$typeof: Symbol;
@@ -16,3 +18,5 @@ declare namespace jest {
     toHaveStyleRule(property: string, value?: Value, options?: Options): R;
   }
 }
+
+export declare const styleSheetSerializer: Exclude<Plugin, NewPlugin>;

yarn.lock

@@ -1133,6 +1133,11 @@
   resolved "https://registry.yarnpkg.com/@types/normalize-package-data/-/normalize-package-data-2.4.0.tgz#e486d0d97396d79beedd0a6e33f4534ff6b4973e"
   integrity sha512-f5j5b/Gf71L+dbqxIpQ4Z2WlmI/mPJ0fOkGGmFgtb6sAu97EPczzbS3/tJKxmcYDj55OX6ssqwDAWOHIYDRDGA==
 
+"@types/pretty-format@^20.0.1":
+  version "20.0.1"
+  resolved "https://registry.yarnpkg.com/@types/pretty-format/-/pretty-format-20.0.1.tgz#7ce03b403887b087701a2b4534464f48ce7b2f48"
+  integrity sha512-Oh7wnvVUCtVIWnCHQWe9qDZKn0fGyk5AMq99jXml0x39K59P+z9qe31CNRtop9TceCpS7NmoK+J9eGeCnyFgnw==
+
 "@types/stack-utils@^1.0.1":
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/@types/stack-utils/-/stack-utils-1.0.1.tgz#0a851d3bd96498fa25c33ab7278ed3bd65f06c3e"