Update api.md

[Ludovic-Iafrate]

• Typo customizatio ns → customizations
• onNavigation/onWidgetRendered descriptions and anchor links were swapped — both corrected
• Removed 7 broken here links pointing to non-existent sections (#on, #pushEvent, #getLatestEvents, #state, #axios-api, #on-navigation, #on-widget-rendered)
• Added missing blank line before the Pages targets table so it renders correctly
• #sub-navigation-ui cross-link → #sub-navigation (that's where the content lives in capabilities.md)
• #user-profile-header-fields and #custom-list had no target sections — replaced with Documentation coming soon
• Removed duplicate #### Organization chart context heading
• const { Button } → const { IconButton } in the IconButton code example
• Missing comma added after href: '/copy' in the List example
• Restored missing pipe | in the navigationItem.classes table row
• Added #### Typography constants section (values inferred from the CSS typography classes already documented in the file), resolving the broken Typography links in Text and SkeletonTypography option tables
• Cleaned up the gap option column in the FlexBox table