website: Added "Extending gem5 for ARM" to learning gem5 part 1

The URL of this page was also changed to be consistent with other
"learning gem5" resources.
"/extending_configs"->"/documentation/learning_gem5/part1/extending_configs"

Change-Id: Ia6068e7cbe351b9115ed1300c423baee1f85ea07
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5-website/+/31294
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: Jason Lowe-Power <power.jg@gmail.com>
diff --git a/_data/documentation.yml b/_data/documentation.yml
index 55f5c8f..fb4f4d1 100755
--- a/_data/documentation.yml
+++ b/_data/documentation.yml
@@ -197,6 +197,8 @@
           url: /documentation/learning_gem5/part1/gem5_stats
         - page: Using the default configuration scripts
           url: /documentation/learning_gem5/part1/example_configs
+        - page: Extending gem5 for ARM
+          url: /documentation/learning_gem5/part1/extending_configs
 
     - title: Modifying/Extending
       id: part2
diff --git a/_pages/documentation/learning_gem5/part1/extending_configs.md b/_pages/documentation/learning_gem5/part1/extending_configs.md
index 1344593..346b0cb 100644
--- a/_pages/documentation/learning_gem5/part1/extending_configs.md
+++ b/_pages/documentation/learning_gem5/part1/extending_configs.md
@@ -3,7 +3,7 @@
 title: Extending gem5 to run ARM binaries 
 doc: Learning gem5
 parent: pt1
-permalink: /extending_configs/
+permalink: /documentation/learning_gem5/part1/extending_configs
 author: Julian T. Angeles 
 ---