Scroll overflow triggered by long words

[FistMeNaruto]

Bug report

Version

0.14.2

Steps to reproduce

1. Open any VuePress project (https://vuepress.vuejs.org/guide/)
2. Open devtools and edit in a long word inside the content (a URL like https://github.com/vuejs/vuepress/issues/vuepress/issues/vuepress/issues/, for example)

What is expected?

Long word breaking and scrolling working properly:

What is actually happening?

Long word introduces a scroll overflow, which allows the navbar to be scrolled out of the viewport:

The same issue happens when long words are inside the nav menu:

Or section headers:

Other relevant information

• Your OS: Arch linux
• Node.js version: v10.10.0
• Browser version: Chromium 68.0.3440.106
• Is this a global or local install? Local
• Which package manager did you use for the install? Yarn

[ulivz]

See: #824 (review)