Fixed #4671 : Hints & Solution and Concept Card Dark Mode

[MohitGupta121]

Fixed #4671

Explanation

Mockups:

Concept Card Default:
https://xd.adobe.com/view/3dca36c2-5115-419c-b25e-0f10526b077c-6899/screen/2cc59921-923b-43ef-bf11-cf7cc5f7d903/specs/

Concept Card Dark Mode:
https://xd.adobe.com/view/c05e9343-60f6-4c11-84ac-c756b75b940f-950d/screen/2ee531cf-c358-4a7d-b9dd-b772b51c3d3c/specs/

Hint Summary Default:
https://xd.adobe.com/view/3dca36c2-5115-419c-b25e-0f10526b077c-6899/screen/99e9e4c3-6c5e-4c13-a9f2-6b92aee17392/specs/

Hint Summary Dark Mode:
https://xd.adobe.com/view/c05e9343-60f6-4c11-84ac-c756b75b940f-950d/screen/d43c5d96-945a-4b89-9552-c4fb482ce2f2/specs/
https://xd.adobe.com/view/c05e9343-60f6-4c11-84ac-c756b75b940f-950d/screen/a70b76a7-49ae-47b6-b5fe-f148b71ee620/specs/

Solution Summary Default:
https://xd.adobe.com/view/3dca36c2-5115-419c-b25e-0f10526b077c-6899/screen/545c6f32-2fec-4a8b-bb53-cecfb8e52f31/specs/

Solution Summary Dark Mode:
https://xd.adobe.com/view/c05e9343-60f6-4c11-84ac-c756b75b940f-950d/screen/5362a633-73cb-4288-aa7d-8c69e4eef349/specs/
https://xd.adobe.com/view/c05e9343-60f6-4c11-84ac-c756b75b940f-950d/screen/a50b0252-f883-451d-9729-dde8d34e2cc5/specs/

Fixed Hints & Solution and Concept Card Dark Mode

Essential Checklist

• The PR title and explanation each start with "Fix #bugnum: " (If this PR fixes part of an issue, prefix the title with "Fix part of #bugnum: ...".)
• Any changes to scripts/assets files have their rationale included in the PR explanation.
• The PR follows the style guide.
• The PR does not contain any unnecessary code changes from Android Studio (reference).
• The PR is made from a branch that's not called "develop" and is up-to-date with "develop".
• The PR is assigned to the appropriate reviewers (reference).

For UI-specific PRs only

Default - Concept Card	Dark Mode - Concept Card
Default - Hint Summary	Dark Mode - Hint Summary
Default - Solution Summary	Dark Mode - Solution Summary

[rt4914]

@MohitGupta121 PTAL. Thanks.

[rt4914]

LGTM, Thanks.

[MohitGupta121]

Thanks @rt4914,
Can you please assign me next part of this dark mode project in doc.