feat: option for caching transform function

.eslintrc.json

@@ -1,7 +1,8 @@
 {
     "env": {
         "es6": true,
-        "node": true
+        "node": true,
+        "mocha": true
     },
     "extends": "eslint:recommended",
     "parserOptions": {
@@ -25,4 +26,4 @@
             "always"
         ]
     }
-}
+}

README.md

@@ -34,14 +34,16 @@ Or, in the simple case of just a `from` with the default destination, you can us
 
 | Name | Required | Default     | Details                                                 |
 |------|----------|------------ |---------------------------------------------------------|
-| `from` | Y        |             | _examples:_<br>'relative/file.txt'<br>'/absolute/file.txt'<br>'relative/dir'<br>'/absolute/dir'<br>'\*\*/\*'<br>{glob:'\*\*/\*', dot: true}<br><br>Globs accept [minimatch options](https://github.com/isaacs/minimatch) |
-| `to`   | N        | output root if `from` is file or dir<br><br>resolved glob path if `from` is glob | _examples:_<br>'relative/file.txt'<br>'/absolute/file.txt'<br>'relative/dir'<br>'/absolute/dir'<br>'relative/[name].[ext]'<br>'/absolute/[name].[ext]'<br><br>Templates are [file-loader patterns](https://github.com/webpack/file-loader) |
+| `from` | Y |  | _examples:_<br>'relative/file.txt'<br>'/absolute/file.txt'<br>'relative/dir'<br>'/absolute/dir'<br>'\*\*/\*'<br>{glob:'\*\*/\*', dot: true}<br><br>Globs accept [minimatch options](https://github.com/isaacs/minimatch) |
+| `to`   | N | output root if `from` is file or dir<br><br>resolved glob path if `from` is glob | _examples:_<br>'relative/file.txt'<br>'/absolute/file.txt'<br>'relative/dir'<br>'/absolute/dir'<br>'relative/[name].[ext]'<br>'/absolute/[name].[ext]'<br><br>Templates are [file-loader patterns](https://github.com/webpack/file-loader) |
 | `toType` | N | **'file'** if `to` has extension or `from` is file<br><br>**'dir'** if `from` is directory, `to` has no extension or ends in '/'<br><br>**'template'** if `to` contains [a template pattern](https://github.com/webpack/file-loader) | |
 | `context` | N | options.context \|\| compiler.options.context | A path that determines how to interpret the `from` path |
 | `flatten` | N | false | Removes all directory references and only copies file names<br><br>If files have the same name, the result is non-deterministic |
 | `ignore` | N | [] | Additional globs to ignore for this pattern |
 | `transform` | N | function(content, path) {<br>&nbsp;&nbsp;return content;<br>} | Function that modifies file contents before writing to webpack |
 | `force` | N | false | Overwrites files already in compilation.assets (usually added by other plugins) |
+| `cache` | N | false | Enable `transform` caching |
+| `cacheKey` | N | `JSON.stringify({ 'copy-webpack-plugin': version, pattern: pattern, absoluteFrom: file.absoluteFrom, content: content })` | Allows you to override default cache key generator |
 
 #### Available options: