Accessibility: Navbar dropdown can't be used with just a keyboard

[missmatsuko]

• I confirm that this is an issue rather than a question.

Bug report

There doesn't seem to be any way to access dropdown items in the navbar using keyboard navigation.

Steps to reproduce

1. Go to https://vuepress.vuejs.org/
2. Tab through the navbar menu items
3. The navbar menu item with a dropdown ("languages") is completely skipped. There's no way to select a language from the navbar using keyboard navigation.

What is expected?

Someone using a keyboard to navigate the site should be able to access dropdown items (and in this case, change the site's language).

What is actually happening?

Someone using a keyboard to navigate the site can't access dropdown items.

Other relevant information

• Output of npx vuepress info in my VuePress project:

[edisdev]

Hi Sir @f3ltron , I opened pull request for this issue. pr link : #1837

[flozero]

Hello @edisdev i will check for it top !