Move heading-nav gui tests to a dedicated book

Author: ehuss

tests/gui/books/heading-nav/README.md

@@ -0,0 +1,3 @@
+# Heading nav
+
+This GUI test book is used for testing sidebar heading navigation.

tests/gui/books/heading-nav/book.toml

@@ -0,0 +1,2 @@
+[book]
+title = "heading-nav"

tests/gui/books/heading-nav/src/SUMMARY.md

@@ -0,0 +1,8 @@
+# Summary
+
+- [Empty page](empty.md)
+- [Large text before first heading](large-intro.md)
+- [Normal text before first heading](normal-intro.md)
+- [Collapsed headings](collapsed.md)
+- [Headings with markup](markup.md)
+- [Current scrolls to bottom](current-to-bottom.md)

tests/gui/books/test_book/src/headings/collapsed.md renamed to tests/gui/books/heading-nav/src/collapsed.md

@@ -28,13 +28,6 @@
   - [Syntax Highlight](languages/highlight.md)
 - [Rust Specific](rust/README.md)
   - [Rust Codeblocks](rust/rust_codeblock.md)
-- [Heading Navigation](headings/README.md)
-  - [Empty page](headings/empty.md)
-  - [Large text before first heading](headings/large-intro.md)
-  - [Normal text before first heading](headings/normal-intro.md)
-  - [Collapsed headings](headings/collapsed.md)
-  - [Headings with markup](headings/markup.md)
-  - [Current scrolls to bottom](headings/current-to-bottom.md)
 - [Last numbered chapter](last.md)
 
 ---