not work with @Vue/Cli v5

[murashi-sn]

Summary

Now, this plugin doesn't support for Vue/CLI v5. The currently known issues are as follows.

• The external library used internally does not support webpack v5. (https://github.com/numical/style-ext-html-webpack-plugin/issues/54)
• It does not support the Asset Module of webpack v5.
• It is unable to support the version upgrade of webpack-dev-server used internally by webpack v5. (Migration guide)