docs: fix spelling mistakes (#478)

Author: zhnoah

CHANGELOG.md

@@ -44,7 +44,7 @@ All notable changes to this project will be documented in this file. See [standa
 ### Notes
 
 * you don't need `ident` option for loader
-* `Object` syntax for the `plugin` option is soft deprecated, please migrate on `Array` syntax (`plugins: ['postcss-present-env', ['cssnano', options]]`)
+* `Object` syntax for the `plugin` option is soft deprecated, please migrate on `Array` syntax (`plugins: ['postcss-preset-env', ['cssnano', options]]`)
 
 <a name="3.0.0"></a>
 # [3.0.0](https://github.com/postcss/postcss-loader/compare/v2.1.6...v3.0.0) (2018-08-08)

README.md

@@ -71,7 +71,7 @@ module.exports = {
             options: {
               postcssOptions: {
                 plugins: [
-                  'postcss-present-env',
+                  'postcss-preset-env',
                   {
                     // Options
                   },
@@ -335,15 +335,15 @@ module.exports = {
                 parser: 'sugarss',
                 plugins: [
                   ['postcss-short', { prefix: 'x' }],
-                  'postcss-present-env',
+                  'postcss-preset-env',
                 ],
               };
             }
 
             return {
               plugins: [
                 ['postcss-short', { prefix: 'x' }],
-                'postcss-present-env',
+                'postcss-preset-env',
               ],
             };
           },
@@ -384,7 +384,7 @@ module.exports = {
   plugins: [
     // Plugins for PostCSS
     ['postcss-short', { prefix: 'x' }],
-    'postcss-present-env',
+    'postcss-preset-env',
   ],
 };
 ```
@@ -406,7 +406,7 @@ module.exports = (api) => {
       plugins: [
         // Plugins for PostCSS
         ['postcss-short', { prefix: 'x' }],
-        'postcss-present-env',
+        'postcss-preset-env',
       ],
     };
   }
@@ -416,7 +416,7 @@ module.exports = (api) => {
     plugins: [
       // Plugins for PostCSS
       ['postcss-short', { prefix: 'x' }],
-      'postcss-present-env',
+      'postcss-preset-env',
     ],
   };
 };
@@ -431,7 +431,7 @@ module.exports = {
   plugins: {
     // Plugins for PostCSS
     'postcss-short': { prefix: 'x' },
-    'postcss-present-env': {},
+    'postcss-preset-env': {},
   },
 };
 ```