fixup! Handle header width per layout
Serve on-demand multiple locales for individual pages and flavor.

To make a single page available in other locales for the current
flavor, you have to define it in the frontmatter:

  locale: { some_flavor: ['en', 'el'], another_flavor: ['en', 'tr'] }

EXAMPLE

The `feedspec` page is available in 3 languages: ['en', 'el', 'tr'].

For the `skroutz` flavor, the `feedspec` page should be available in
['en', 'el'].
For the `alve` flavor, the `feedspec` page should be available in
['en', 'tr'].

To achieve it, we have to declare at the frontmatter of:

- `feedspec.en.html.erb`
  locale: { alve: ['en', 'tr'], skroutz: ['en', 'el'] }

- `feedspec.tr.html.erb`
  locale: { alve: ['en', 'tr'] }

- `feedspec.el.html.erb`
  locale: { skroutz: ['en', 'el'] }