move react-helmet to optional dependencies

Signed-off-by: Dmitriy Nevzorov <[email protected]>

Author: jimmyn

README.md

@@ -224,7 +224,7 @@ const SpanishAboutLink = () => (
 
 `Helmet` component is identical to [`gatsby-plugin-react-helmet`](https://www.gatsbyjs.org/packages/gatsby-plugin-react-helmet) component but also provides language related metatags (alternative and canonical links)
 
-**Note!** You need to provide `siteUrl` in plugin options for it to work properly
+**Note!** To use it you need to have `react-helmet` dependency installed. You also need to provide `siteUrl` in plugin options for it to work properly.
 
 ### `I18nextContext`
 

package.json

@@ -45,7 +45,6 @@
     "@babel/cli": "^7.10.1",
     "@types/bluebird": "^3.5.32",
     "@types/react": "^16.9.35",
-    "@types/react-helmet": "^6.0.0",
     "babel-preset-gatsby-package": "^0.4.2",
     "gatsby": "^2.22.12",
     "husky": "^4.2.5",
@@ -54,20 +53,23 @@
     "release-it": "^13.6.1",
     "typescript": "^3.9.3",
     "i18next": "^19.4.5",
-    "react-i18next": "^11.5.0"
+    "react-i18next": "^11.5.0",
+    "@types/react-helmet": "^6.0.0"
   },
   "dependencies": {
     "bluebird": "^3.7.2",
     "browser-lang": "^0.1.0",
-    "glob": "^7.1.6",
-    "react-helmet": "^6.0.0"
+    "glob": "^7.1.6"
   },
   "peerDependencies": {
     "gatsby": "^2.2.0",
     "react": "^16.12.0",
     "i18next": "^19.4.5",
     "react-i18next": "^11.5.0"
   },
+  "optionalDependencies": {
+    "react-helmet": "^6.0.0"
+  },
   "husky": {
     "hooks": {
       "pre-commit": "pretty-quick --staged"