[Doc] Update customize doc as bootstrap ways

[cavasinf]

Description

Update customize doc as bootstrap ways

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• I updated the documentation (see here)
• I agree that this code will be published under the MIT license

[kevinpapst]

This version sounds better.

I wonder how much this might change with the upcoming release of:
https://tabler-git-dev-props-tabler-io.vercel.app/?theme-primary=red&theme-font=monospace&theme-radius=2&theme-base=neutral

CSS variables might become the simpler solution, so people don't need the additional build step

[cavasinf]

CSS variables might become the simpler solution, so people don't need the additional build step

Agree, even more with the Symfony Asset Mapper, which encourages a "no-build" approach (no webpack/no Node) using raw JS and CSS, without the need for TS or SCSS files.