feat(forms): Adding dropdown category and related sub question type

[ccailly]

Q	A
Bug fix?	no
New feature?	yes
BC breaks?	no
Deprecations?	no
Tests pass?	yes
Fixed tickets

Added Dropdown category and related sub-question type : Dropdown

Form editor view :

Form end user view :

[AdrienClairembault]

Two small bugs I've found:

1) Wrong input name

Should be answers_141 since we switched to the new format.
This mean answers are not taken into account for this question type.

2) Invalid order

It seems the dropdown is not refreshed after options order are modified using drag and drop.

The "old" order is still displayed until we do another action like changing the default value.

[orthagh]

(opinion based on the provided screenshots)
I feel the design choice when checking multiple flag to switch between radio or checkboxes for options lead to a bad understanding. At least it took a few seconds to understand the options will be displayed in a real dropdown. I almost made a comment about why call it dropdown.

I think in this particular case, you should not decorate options at all. More, there is the drag icon, so 2 icons on the left of the options

Ideas for alternative ux:

• select2 tokenisation (may not work without multiple select)
• modal with a [new option] link right to the dropdown
• keep the same design (without decoration), but make options list like it's the dropdown opened (check this link)

[ccailly]