[DOCS] Creates custom landing page for the Rust client book

[szabosteve]

Overview

This PR adds a new landing page to the Rust client book so it will be more in line with the main docs landing page, the ES guide landing page, and the Kibana guide landing page.

• Current Rust docs landing page

The content can be easily modified based on feedback.

[szabosteve]

@swallez Sure, it makes sense! I'll modify the description accordingly.

[szabosteve]

💚 All backports created successfully

Status	Branch	Result
✅	8.7

Questions ?

Please refer to the Backport tool documentation