message: Docs: Mention 'alignY' in Icon migration guide
diff: @@ -7,6 +7,7 @@ Please note that this is a breaking change to our design language. When migratin
  - When inside a `Text` or `Heading` component, icons inherit the `size` and `tone` accordingly. As a result it's likely that you will be able to remove custom icon sizing styles in your application.
  - If an icon is not in a `Text` or `Heading` the standard typographic hierarchy is available for sizing, eg. `size={'xsmall' | 'small' | 'standard' | 'large'}`) and will use the defined line height. Heading-sized icons are not supported outside of a heading context.
  - If you need a custom icon size, use `size="fill"` to make the icon fill its container.
  +- If the vertical alignment of the icon doesn't look quite right, consider using the `alignY` prop which supports a value of `"uppercase"` or `"lowercase"`.
  - No longer accepts arbitrary DOM properties, e.g. `className`, `svgClassName`, etc.
  ### Diff
  