Allow using strings in head config option

[sergeymorkovkin]

Feature request

What problem does this feature solve?

Simplifies adding page tags to end-users. For example, favicon generators provides a bunch of head tags, which are ready to be injected. The thing is now developer has to parse these HTML tags into consumable object like ['meta', { 'http-equiv': 'X-UA-Compatible', 'content': 'IE=edge' }]. This doesn't help at all.

What does the proposed API look like?

Allow pure HTML strings in the head configuration option.

How should this be implemented in your opinion?

Simply add list item type checking. Should consider SSR renderer and vuepress-html-webpack-plugin.

Are you willing to work on this yourself?

I might if you confirm this is welcome.