docs: Documentation restructure

- Change main index structure
- Sort out integration and porting guidelines
- Resort table with releases
- Add Tools section. To be adjusted further for tf-m-tools

Intention to minimise files movement to simplify review process.
Affected files shall be moved later after the new structure agreement.

Signed-off-by: Anton Komlev <anton.komlev@arm.com>
Change-Id: I0352bebabe09d4f7b5e8848ee620c0cea6881c94
diff --git a/docs/contributing/index.rst b/docs/contributing/index.rst
index e5f9c66..71ba543 100644
--- a/docs/contributing/index.rst
+++ b/docs/contributing/index.rst
@@ -3,10 +3,14 @@
 
 .. toctree::
     :maxdepth: 1
-    :glob:
+    :titlesonly:
 
-    *
-
+    The process <contributing_process>
+    Code review <code_review_guide>
+    Maintainers and Owners <maintainers>
+    coding_guide
+    Documentation <doc_guidelines>
+    Design proposal <tfm_design_proposal_guideline>
 
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