To have a clean break for upcoming changes we will duplicate
index.less into legacy.less and create a new module to clearly
separate new styles from old.
The preferred name however does come with some caching challenges.
Cached HTML served to anons will continue to load the style module
`skins.vector.styles` for a period of 1-4 weeks
Provided we are careful with our changes during this period this
should be okay.
Change-Id: If32b59036e5cd62cbb804944ca93fa1a101c5129
