Move react-router-dom as an explicit dependency

While `react-router-dom` is not always required at runtime (only really requested when using `<SecureRoute />`), having it defined as a peer dependency raise issues for any user wanted to move to next majors of `react-router-dom` and not relying on `<SecureRoute />`.

Indeed for such users of `okta-react`, WebPack and other bundlers will fail to build the project because of the import of `useMatchRoute` not being part of the new major of `react-router-dom`. While it probably make a bit of sense whne you use `<SecureRoute />`, having your build broken because of it while you don't need it at all is strange. By moving the library as a clear dependency, `okta-react` wil always pull the right version and stop making user's builds fail.

package.json

@@ -40,13 +40,12 @@
   },
   "dependencies": {
     "@babel/runtime": "^7.11.2",
-    "@okta/okta-auth-js": "^4.8.0"
+    "@okta/okta-auth-js": "^4.8.0",
+    "react-router-dom": "^5.1.0"
   },
   "peerDependencies": {
-    "@types/react-router-dom": "^5.1.6",
     "react": ">=16.8.0",
-    "react-dom": ">=16.8.0",
-    "react-router-dom": ">=5.1.0"
+    "react-dom": ">=16.8.0"
   },
   "devDependencies": {
     "@babel/cli": "^7.11.6",
@@ -104,4 +103,4 @@
     "./",
     "test/e2e/harness"
   ]
-}
+}