[3.x] Add selectable prop on VueSelect component

[kallefrombosnia]

Description

Twill uses Vue Select component which is extended in the Twill vselect component. From 3.3.0 Vue Select, there is a new component prop selectable which allows us to set the disabled state on specific select options.

If we don't pass any value (default case), all options would be available in the select.

Usage:
form.blade.php

@formField('select', [
    'name' => 'office',
    'label' => 'Office',
    'placeholder' => 'Select an office',
    'options' => [
        [
            'value' => 1,
            'label' => 'New York'
        ],
        [
            'value' => 2,
            'label' => 'London'
        ],
        [
            'value' => 3,
            'label' => 'Berlin',
            'selectable' => false
        ]
    ]
])

Note on the third item we have new property selectable which allows us to set a boolean value regarding should be option selectable or not.

It's hard to see the change here since Lightshot doesn't capture the icon which is shown over the non-selectable option.

Also, it creates some CSS class conflict in which the -1 element keeps a hover state.
I will inspect this and create documentation in the next commits.

Related Issues

Fixes #1266

[codecov]

Codecov Report

Merging #1619 (da47346) into 3.x (acbcf55) will increase coverage by 0.00%.
The diff coverage is 0.00%.

@@            Coverage Diff            @@
##                3.x    #1619   +/-   ##
=========================================
  Coverage     56.33%   56.33%           
- Complexity     3020     3024    +4     
=========================================
  Files           239      239           
  Lines          9248     9255    +7     
=========================================
+ Hits           5210     5214    +4     
- Misses         4038     4041    +3     

Impacted Files	Coverage Δ
src/Services/Forms/Option.php	0.00% <0.00%> (ø)
src/TwillRoutes.php	77.77% <0.00%> (-0.49%)	⬇️
src/Models/Behaviors/HasTranslation.php	20.00% <0.00%> (-0.34%)	⬇️
src/Helpers/Capsule.php	74.28% <0.00%> (+0.40%)	⬆️

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[haringsrob]

👍
Looks good and simple enough. Please however, for now do not included the compiled css/js as we are still doing many changes and want to avoid conflicts there.

[kallefrombosnia]

@haringsrob Thanks, compiled stuff is removed from PR.

Also, documentation is added, which looks like this. I have separated them from the main prop list since this is an item prop.
Let me know if this is good.

[haringsrob]

I have updated the pr to change the form doc and also added this selectable prop to the formbuilder option object.