fix missing `extends` for custom elements

content/docs/web-components.md

@@ -42,7 +42,7 @@ function BrickFlipbox() {
 ## Using React in your Web Components
 
 ```javascript
-class XSearch {
+class XSearch extends HTMLElement {
   connectedCallback() {
     const mountPoint = document.createElement('span');
     this.attachShadow({ mode: 'open' }).appendChild(mountPoint);

yarn.lock

@@ -2332,14 +2332,6 @@ create-hmac@^1.1.0, create-hmac@^1.1.2, create-hmac@^1.1.4:
     safe-buffer "^5.0.1"
     sha.js "^2.4.8"
 
-create-react-class@^15.6.0:
-  version "15.6.2"
-  resolved "https://registry.yarnpkg.com/create-react-class/-/create-react-class-15.6.2.tgz#cf1ed15f12aad7f14ef5f2dfe05e6c42f91ef02a"
-  dependencies:
-    fbjs "^0.8.9"
-    loose-envify "^1.3.1"
-    object-assign "^4.1.1"
-
 cross-env@^3.1.1:
   version "3.2.4"
   resolved "https://registry.yarnpkg.com/cross-env/-/cross-env-3.2.4.tgz#9e0585f277864ed421ce756f81a980ff0d698aba"
@@ -4438,7 +4430,7 @@ graphql-skip-limit@^1.0.5:
   dependencies:
     babel-runtime "^6.26.0"
 
-graphql@^0.10.3, graphql@^0.10.5:
+graphql@0.10.5, graphql@^0.10.3, graphql@^0.10.5:
   version "0.10.5"
   resolved "https://registry.yarnpkg.com/graphql/-/graphql-0.10.5.tgz#c9be17ca2bdfdbd134077ffd9bbaa48b8becd298"
   dependencies:
@@ -7755,16 +7747,7 @@ react-deep-force-update@^2.0.1:
   version "2.0.1"
   resolved "https://registry.yarnpkg.com/react-deep-force-update/-/react-deep-force-update-2.0.1.tgz#4f7f6c12c3e7de42f345992a3c518236fa1ecad3"
 
-react-dom@^15.6.0:
-  version "15.6.2"
-  resolved "https://registry.yarnpkg.com/react-dom/-/react-dom-15.6.2.tgz#41cfadf693b757faf2708443a1d1fd5a02bef730"
-  dependencies:
-    fbjs "^0.8.9"
-    loose-envify "^1.1.0"
-    object-assign "^4.1.0"
-    prop-types "^15.5.10"
-
-react-dom@^16.0.0:
+react-dom@16.0.0, react-dom@^15.6.0, react-dom@^16.0.0:
   version "16.0.0"
   resolved "https://registry.yarnpkg.com/react-dom/-/react-dom-16.0.0.tgz#9cc3079c3dcd70d4c6e01b84aab2a7e34c303f58"
   dependencies:
@@ -7827,17 +7810,7 @@ react-side-effect@^1.1.0:
     exenv "^1.2.1"
     shallowequal "^1.0.1"
 
-react@^15.6.0:
-  version "15.6.2"
-  resolved "https://registry.yarnpkg.com/react/-/react-15.6.2.tgz#dba0434ab439cfe82f108f0f511663908179aa72"
-  dependencies:
-    create-react-class "^15.6.0"
-    fbjs "^0.8.9"
-    loose-envify "^1.1.0"
-    object-assign "^4.1.0"
-    prop-types "^15.5.10"
-
-react@^16.0.0:
+react@16.0.0, react@^15.6.0, react@^16.0.0:
   version "16.0.0"
   resolved "https://registry.yarnpkg.com/react/-/react-16.0.0.tgz#ce7df8f1941b036f02b2cca9dbd0cb1f0e855e2d"
   dependencies: