bug #10314 [Docs] Update "Customizing Forms" (Tomanhez)
bug #10314 [Docs] Update "Customizing Forms" (Tomanhez)

This PR was merged into the 1.3 branch.

Discussion
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| Q               | A
| --------------- | -----
| Branch?         | 1.3
| Bug fix?        | yes
| New feature?    | no
| BC breaks?      | no
| Deprecations?   | no/
| License         | MIT



Commits
-------

607a11f390221dbc0d167c7e8e3d997e7be9b1a9 update customization guide form

kayue/Sylius,antonioperic/Sylius,Arminek/Sylius,101medialab/Sylius,101medialab/Sylius,lchrusciel/Sylius,pjedrzejewski/Sylius,GSadee/Sylius,kayue/Sylius,Sylius/Sylius,loic425/Sylius,mbabker/Sylius,diimpp/Sylius,pjedrzejewski/Sylius,Zales0123/Sylius,GSadee/Sylius,lchrusciel/Sylius,loic425/Sylius,Brille24/Sylius,SyliusBot/Sylius,Sylius/Sylius,Brille24/Sylius,Arminek/Sylius,itinance/Sylius,SyliusBot/Sylius,antonioperic/Sylius,Brille24/Sylius,mbabker/Sylius,pjedrzejewski/Sylius,kayue/Sylius,itinance/Sylius,SyliusBot/Sylius,foobarflies/Sylius,loic425/Sylius,Brille24/Sylius,foobarflies/Sylius,pjedrzejewski/Sylius,101medialab/Sylius,foobarflies/Sylius,mbabker/Sylius,pamil/Sylius,GSadee/Sylius,lchrusciel/Sylius,mbabker/Sylius,itinance/Sylius,diimpp/Sylius,foobarflies/Sylius,itinance/Sylius,Zales0123/Sylius,Arminek/Sylius,antonioperic/Sylius,Sylius/Sylius,diimpp/Sylius,pamil/Sylius,pamil/Sylius,Zales0123/Sylius