Upgrade `joi`

[HsuTing]

The Issues page for this repository is not a support forum, it is for reporting potential bugs in this module, which
composes webpack-hot-middleware and webpack-dev-middle for use with koa2.
If you have arrived here because you cannot get webpack-hot-middleware
or webpack-dev-middleware working, please review the documentation
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• Node Version: v11.12.0
• NPM Version: v6.9.0
• koa Version: v2.7.0
• koa-wepback Version: v5.2.2

If you have a large amount of code to share which demonstrates the problem you're experiencing, please provide a link to your
repository rather than pasting code. Otherwise, please paste relevant short snippets below.

// webpack.config.js

// app.js

Expected Behavior

No warning

Actual Behavior

warning koa-webpack > joi@14.3.1: This module has moved and is now available at @hapi/joi. Please update your dependencies as this version is no longer maintained an may contain bugs and security issues.
warning koa-webpack > joi > topo@3.0.3: This module has moved and is now available at @hapi/topo. Please update your dependencies as this version is no longer maintained an may contain bugs and security issues.
warning koa-webpack > joi > hoek@6.1.3: This module has moved and is now available at @hapi/hoek. Please update your dependencies as this version is no longer maintained an may contain bugs and security issues.
warning koa-webpack > joi > topo > hoek@6.1.3: This module has moved and is now available at @hapi/hoek. Please update your dependencies as this version is no longer maintained an may contain bugs and security issues.

How can we reproduce the behavior?

yarn add koa-webpack

[shellscape]

This is a non-issue as warnings do not hamper functionality. koa-webpack gets periodic dependency updates, and this will likely be resolved then.