Make the vscroll API documentation complete and self-contained #77

Problem

The core documentation currently covers only the basic integration flow. Important parts of the public API are either undocumented or delegated to external sources:

• Adapter API documentation points to ngx-ui-scroll;
• settings and development settings are not documented systematically;
• Routines documentation points directly to TypeScript source files;
• some links reference old source versions;
• consumer examples effectively act as the source of truth for core behavior.

This makes it difficult to use vscroll directly and obscures differences between the core API and framework-specific consumers—for example, core Reactive objects versus RxJS entities in ngx-ui-scroll.

Goal

Provide complete documentation for the public vscroll API within this repository. Consumer documentation may remain as supplementary material, but it should no longer be required to understand or use the core library.