Enable 'Sticky Scroll' for gherkins feature files

### 🤔 What's the problem you're trying to solve?

VSCode has the feature called 'Sticky Scroll'. See **[here](https://code.visualstudio.com/docs/getstarted/userinterface#_sticky-scroll)**.

It would be awesome if this would work for gherkin's *.feature files too.

### ✨ What's your proposed solution?

Actually, I am not familiar with what needs to be done to make it work. But maybe you just have to provide some more semantic/context to the editor, comparable to what gets provided to the code-highlighting feature.

### ⛏ Have you considered any alternatives or workarounds?

_No response_

### 📚 Any additional context?

_No response_

Start with the extension's existing handling of *.feature files and compare it with the VS Code Sticky Scroll documentation linked in the issue. Determine what semantic or contextual information the editor requires, then verify that headings in Gherkin feature files appear in Sticky Scroll as expected.

Written by the indexing model from the issue text.