Added missing dev dependency.

package.json

@@ -41,12 +41,13 @@
         "@types/react-helmet": "5.0.7",
         "@types/react-router": "4.4.3",
         "@types/react-router-dom": "4.3.1",
-        "cross-env": "^5.2.0",
+        "cross-env": "5.2.0",
         "node-sass": "4.11.0",
         "npm-run-all": "4.1.5",
         "react-scripts": "2.1.1",
         "tslint": "5.12.0",
-        "tslint-plugin-prettier": "^2.0.1",
+        "tslint-config-prettier": "1.18.0",
+        "tslint-plugin-prettier": "2.0.1",
         "tslint-react": "3.6.0",
         "typescript": "3.2.2",
         "typescript-plugin-css-modules": "1.0.5",

yarn.lock

@@ -2935,7 +2935,7 @@ [email protected]:
     fbjs "^0.8.0"
     gud "^1.0.0"
 
-cross-env@^5.2.0:
+[email protected]:
   version "5.2.0"
   resolved "https://registry.yarnpkg.com/cross-env/-/cross-env-5.2.0.tgz#6ecd4c015d5773e614039ee529076669b9d126f2"
   integrity sha512-jtdNFfFW1hB7sMhr/H6rW1Z45LFqyI431m3qU6bFXcQ3Eh7LtBuG3h74o7ohHZ3crrRkkqHlo4jYHFPcjroANg==
@@ -10880,7 +10880,12 @@ tslib@^1.7.1, tslib@^1.8.0, tslib@^1.8.1, tslib@^1.9.0:
   resolved "https://registry.yarnpkg.com/tslib/-/tslib-1.9.3.tgz#d7e4dd79245d85428c4d7e4822a79917954ca286"
   integrity sha512-4krF8scpejhaOgqzBEcGM7yDIEfi0/8+8zDRZhNZZ2kjmHJ4hv3zCbQWxoJGz1iw5U0Jl0nma13xzHXcncMavQ==
 
-tslint-plugin-prettier@^2.0.1:
+[email protected]:
+  version "1.18.0"
+  resolved "https://registry.yarnpkg.com/tslint-config-prettier/-/tslint-config-prettier-1.18.0.tgz#75f140bde947d35d8f0d238e0ebf809d64592c37"
+  integrity sha512-xPw9PgNPLG3iKRxmK7DWr+Ea/SzrvfHtjFt5LBl61gk2UBG/DB9kCXRjv+xyIU1rUtnayLeMUVJBcMX8Z17nDg==
+
+[email protected]:
   version "2.0.1"
   resolved "https://registry.yarnpkg.com/tslint-plugin-prettier/-/tslint-plugin-prettier-2.0.1.tgz#95b6a3b766622ffc44375825d7760225c50c3680"
   integrity sha512-4FX9JIx/1rKHIPJNfMb+ooX1gPk5Vg3vNi7+dyFYpLO+O57F4g+b/fo1+W/G0SUOkBLHB/YKScxjX/P+7ZT/Tw==