This is the client-side implementation of allowing a user to save their custom role for their community. Since `CreateRolesHeaderRightButton` needs access to both the `roleName` and the
`rolePermissions`, it made sense to include those in the navigation route params, and I can pull them directly from there. That's why the `React.useEffect` hook updates the params.
This is also useful because once I work on the `edit_role` flow, I can default the `roleName` and `rolePermissions` to the existing name/permissions to 'pre-fill' the info for the client.
Depends on D8420
[[ https://linear.app/comm/issue/ENG-4174/use-createrolesscreenheaderrightbutton-to-save-a-new-role | ENG-4174 ]].