refactor(baker): allow bake dirs for all gdoc types

[mlbrgl]

This is in preparation of baking author pages under /team.

This PR reuses the getCanonicalUrl logic to build a bake path for all gdocs.

• test article: http://staging-site-generic-bake-dir/launching-data-insights
• test data insight: http://staging-site-generic-bake-dir/data-insights/extreme-poverty-in-china-has-been-almost-eliminated-first-in-rural-then-in-urban-regions

[mlbrgl]

• Author pages: pre-launch additions #3484
• Author pages: design review #3348
• feat(author): bake author gdocs #3322
• Add author work #3257
• Add author header #3256
• refactor(baker): allow bake dirs for all gdoc types #3310 👈
• fix(r&w): tablet styles for first featured article #3302
• master

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[marcelgerber]

Nice way of building on #3280, go for it! 🙌🏻