Docs: reordered index grid (#345)

* reordered index to have separate install card, and diataxis grid

* add Tutorials folder

* Explain that tutorials/README.md is just a blank placeholder file.  Can be removed in future.

* Update docs/index.rst

Co-authored-by: Leo Paoletti <164940351+lpaoletti@users.noreply.github.com>

* changed to quick start (no hyphen)

* missed index.rst for quick start edit

* change text to Using rocDecode

---------

Co-authored-by: Leo Paoletti <164940351+lpaoletti@users.noreply.github.com>

docs/sphinx/_toc.yml.in

@@ -9,11 +9,26 @@ subtrees:
 - caption: Install
   entries:
   - file: install/quick-start.rst
-    title: Quick-start
+    title: Quick start
   - file: install/install.md
     title: Installation guide
 
-- caption: API reference
+- caption: Tutorials
+  entries:
+  - url: https://github.com/ROCm/rocDecode/tree/develop/samples
+    title: GitHub samples
+
+- caption: How to
+  entries:
+  - file: how-to/using-rocdecode.rst
+    title: Using rocDecode
+
+- caption: Conceptual
+  entries:
+  - file: conceptual/video-decoding-pipeline.rst
+    title: Video decoding pipeline
+
+- caption: Reference
   entries:
   - file: doxygen/html/files
     title: API library
@@ -22,21 +37,6 @@ subtrees:
   - file: doxygen/html/annotated
     title: Data structures
 
-- caption: How to
-  entries:
-  - file: how-to/using-rocdecode.rst
-    title: Use rocDecode
-
-- caption: Conceptual
-  entries:
-  - file: conceptual/video-decoding-pipeline.rst
-    title: Video decoding pipeline
-
-- caption: Tutorials
-  entries:
-  - url: https://github.com/ROCm/rocDecode/tree/develop/samples
-    title: GitHub samples
-
 - caption: About
   entries:
   - file: license.md