Refresh: CSS base bundle clean up

[wen-2018]

Description

Currently, the m24 base bundle doesn't include existing component styles. We should update it to include common styles in protocol-mozilla, but with imports of the new nav / footer, home and new styles instead of the old ones, avoiding serving redundant styles to users when the brand refresh switch is on:

{% if switch('m24-base') and LANG.startswith('en-') %}
  {{ css_bundle('m24-base') }}
{% else %}
  {{ css_bundle('protocol-mozilla') }}
{% endif %}

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