Wide screen onboarding: center text, limit width

[jpelgrom]

Summary

Quick improvements to the onboarding for wide screens:

• Center align text on the initial screen to prevent odd alignment of a single line
• Limit the content width on onboarding screens to 600dp centered, like other step flows/bottom sheets (still wide-ish but let's stay consistent)
• Update padding values on initial onboarding screen to match 8dp grid used in all other places

Screenshots

Before	After
(not taken but you get the idea)
(also not taken but you get the idea)

Link to pull request in Documentation repository

n/a

Any other notes