Update contibutor guidelines with rules for header guards
- Includes an example

Resolves: [COMPMID-5867]

Signed-off-by: Mohammed Suhail Munshi <MohammedSuhail.Munshi@arm.com>
Change-Id: I02c0cafecf56e9cbaf9e8284d43f8ef87af8f4d8
Reviewed-on: https://eu-gerrit-1.euhpc.arm.com/c/VisualCompute/ComputeLibrary/+/510081
Comments-Addressed: bsgcomp <bsgcomp@arm.com>
Tested-by: bsgcomp <bsgcomp@arm.com>
Reviewed-by: Viet-Hoa Do <viet-hoa.do@arm.com>
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/9441
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Pablo Marquez Tello <pablo.tello@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Benchmark: Arm Jenkins <bsgcomp@arm.com>
diff --git a/docs/contributor_guide/contribution_guidelines.dox b/docs/contributor_guide/contribution_guidelines.dox
index d028734..30ee41a 100644
--- a/docs/contributor_guide/contribution_guidelines.dox
+++ b/docs/contributor_guide/contribution_guidelines.dox
@@ -1,5 +1,5 @@
 ///
-/// Copyright (c) 2019-2022 Arm Limited.
+/// Copyright (c) 2019-2023 Arm Limited.
 ///
 /// SPDX-License-Identifier: MIT
 ///
@@ -240,6 +240,18 @@
 };
 @endcode
 
+- In header files, use header guards that use the full file path from the project root and prepend it with "ACL_"
+
+@code{cpp}
+// For File arm_compute/runtime/NEON/functions/NEBatchNormalizationLayer.h
+#ifndef ACL_ARM_COMPUTE_RUNTIME_NEON_FUNCTIONS_NEBATCHNORMALIZATIONLAYER
+#define ACL_ARM_COMPUTE_RUNTIME_NEON_FUNCTIONS_NEBATCHNORMALIZATIONLAYER
+.
+.
+.
+#endif /* ACL_ARM_COMPUTE_RUNTIME_NEON_FUNCTIONS_NEBATCHNORMALIZATIONLAYER */
+@endcode
+
 - Use quotes instead of angular brackets to include local headers. Use angular brackets for system headers.
 - Also include the module header first, then local headers, and lastly system headers. All groups should be separated by a blank line and sorted lexicographically within each group.
 - Where applicable the C++ version of system headers has to be included, e.g. cstddef instead of stddef.h.