Avoid bundling all of octicons-react

[mxstbr]

Looking at @primer/components on bundlephobia, it's massive (40kB min+gzip), mainly because it bundles all of @githubprimer/octicons-react in the StyledOcticon component.

While we are definitely going to use some Octicons, they will only be on specific views and codesplit, bundling all of them into our main bundle is not ideal. Is there a way to lazy load the octicons as they are used or something like that?

EDIT: Found a workaround in #456 by importing specific components. It would still be good to see this solved by default.

[shawnbot]

Yeesh, good catch. Can we avoid bundling it simply by declaring it as external in our rollup config?

[emplums]

@shawnbot I tried doing that and it looks like the bundle size is the same :/

[emplums]

Making it external worked, turns out our bundle size reporting in our dist command was just broken :)

Fixed in #459