[docs] Add blurb about current bp6 namespace prefix to docs

[ggdouglas]

Changes

• Adds blurb that explicitly documents the bp6 namespace prefix.
• Added to this page: https://blueprintjs.com/docs/#core/classes
• Added under: Classes → Namespacing → Current namespace prefix

Before / After

---

Current namespace prefix

Blueprint v6 uses the bp6- prefix for all CSS classes. For example, Button components have the class .bp6-button, Cards have .bp6-card, etc. This prefix changes with each major version of Blueprint (e.g., v5 used bp5-, v6 uses bp6-).

When writing custom styles that target Blueprint components, you should reference the namespace using the $ns Sass variable rather than hardcoding the prefix:

@use "@blueprintjs/core/lib/scss/variables.scss" as bp;

.my-class .#{bp.$ns}-button {
    // Custom styles for Blueprint buttons within .my-class
    background-color: red;
}

---

Checklist

• Includes tests
• Update documentation

[svc-palantir-github]

Add blurb about current bp6 namespace prefix to docs

Build artifact links for this commit: documentation | landing | table | demo

This is an automated comment from the deploy-preview CircleCI job.

[svc-palantir-github]

Escape `@use` syntax in docs to avoid clash with docs `@tag`

Build artifact links for this commit: documentation | landing | table | demo

This is an automated comment from the deploy-preview CircleCI job.

[svc-palantir-github]

Add `@use` to reserved tags

Build artifact links for this commit: documentation | landing | table | demo

This is an automated comment from the deploy-preview CircleCI job.