fix: auto install plugin in browser

scripts/rollup.config.js

@@ -85,6 +85,7 @@ function rollupConfig({
       // replaceConfig needs to have some values
       'const polyfill = process.env.NODE_ENV === \'test\'': 'const polyfill = true',
       'process.env.VERSION': `"${version}"`,
+      'process.client' : isBrowserBuild ? 'true' : 'false',
       'process.server' : isBrowserBuild ? 'false' : 'true',
       /* remove unused stuff from deepmerge */
       // remove react stuff from is-mergeable-object

src/index.js

@@ -5,6 +5,7 @@ import { setOptions } from './shared/options'
 import $meta from './shared/$meta'
 import generate from './server/generate'
 import { hasMetaInfo } from './shared/meta-helpers'
+import { isUndefined } from './utils/is-type'
 
 /**
  * Plugin install function.
@@ -25,6 +26,14 @@ function install (Vue, options) {
   Vue.mixin(createMixin(Vue, options))
 }
 
+if (process.client) {
+  // automatic install
+  if (!isUndefined(window) && !isUndefined(window.Vue)) {
+    /* istanbul ignore next */
+    install(window.Vue)
+  }
+}
+
 export default {
   version,
   install,