Replace Webpack MIX with original Webpack

Problem/Motivation

Vartheme BS5 using webpack mix and laravel mix to compile scss.
It's better to use the default webpack with post-css and scss loader to compile scss.

Proposed resolution

• Replace webpack.mix.js with webpack.config.js.
• Add webpack.config.build.js file for build configuration.
• Add webpack.config.dev.js file for dev configuration.

Remaining tasks

• ✅ File an issue about this project
• ✅ Addition/Change/Update/Fix to this project
• ✅ Testing to ensure no regression
• ➖ Automated unit/functional testing coverage
• ➖ Developer Documentation support on feature change/addition
• ➖ User Guide Documentation support on feature change/addition
• ➖ Accessibility and Readability
• ✅ Code review from 1 Varbase core team member
• ✅ Full testing and approval
• ✅ Credit contributors
• ✅ Review with the product owner
• ✅ Update Release Notes and Update Helper on new feature change/addition
• ✅ Release varbase-10.0.0-alpha1 → , vartheme_bs5-2.0.0-alpha2 →

Varbase update type

• ✅ No Update
• ➖ Optional Update
• ➖ Forced Update
• ➖ Forced Update if Unchanged

User interface changes

• N/A

API changes

• N/A

Data model changes

• N/A

Release notes snippet

• Issue #3319381 → by Abdullah Yassin → : Replaced Webpack MIX with original Webpack