Improve style

[tagliala]

Contains changes (some are opinionated) for better integration with Bootstrap 4

Add stylelint

• Same configuration as Boostrap
• Allows BEM-like selectors
• Some rules have been disabled ad-hoc

Move layout to its own partial

Allow users to customize individual components or to use just one of them (e.g., "single" and "layout" when "multiple" is not needed)

Improve single component

• Lint style
• Use $input-color to match Bootstrap
• Use $input-padding-x to match Bootstrap
• Use $input-placeholder-color to match Bootstrap

Improve multiple component

• Lint style
• Use $input-padding-x to match Bootstrap
• Use $input-color to match Bootstrap

Improve layout partial

• Lint style
• Use border-bottom-radius mixin
• Fix border radius on open containers
• Use color-yiq mixin to pick the correct color in highlighted choice
• Use $input-padding-y and $input-padding-x
• Use $input-bg as base color to darken for selected choice

Fix cursor on disabled elements

Reproducible with Chrome 88 on macOS

Before

After

[ttskch]

@tagliala Thanks for your contribution! I think your PR is great. But I've just pushed some commits, so could you please resolve the conflicts? 🙇

[tagliala]

Hi @ttskch

I've rebased and I've added a fix for cursor in disabled elements

I've also add stylelint with (almost) the same configuration as bootstrap (I've included a regex to allow BEM-like selectors)

[ttskch]

@tagliala Thanks a lot!