feat(searchbar): add --box-shadow variable to style searchbar input

[antoinecfmws]

We would like to style the box-shadow property in searchbar and give the parent the ability to control it.

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
• Build (npm run build) was run locally and any changes were pushed
• Lint (npm run lint) has passed locally and any fixes were made for failures

(Sorry running on a windows box and unable to run "sass")

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe): SCSS File Update to expose a css variable / property for searchbar

What is the current behavior?

Issue Number: N/A
The behaviour modification is simply to expose a css variable that is currently not exposed and set by default for md styles on component searchbar.

What is the new behavior?

• This PR exposes --box-shadow so that we can have control over that property
• Users using md style for searchbar will be able to set the box-shadow on the input with class "searchbar-input"

Does this introduce a breaking change?

• Yes
• No

N/A

Other information

N/A

[brandyscarney]

Thanks for the PR! I moved the box-shadow to the main file so that it will apply for both modes.

@liamdebeasi I had to remove contain: strict so the ios input could receive a box shadow. Let me know if you foresee issues with this.

[liamdebeasi]

Merged. Thank you!