chore: update rollup config

[joshblack]

The @primer/styled-octicons step in the react job is currently failing: https://github.com/primer/octicons/actions/runs/3208168870/jobs/5243790946

This PR updates the rollup config for lib/styled_octicons to resolve presets relative to the package instead of the files. This should address the error where the babel rollup plugin is unable to find the presets/plugins that it's looking for.

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Latest commit: 1bfd7f3

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