Add clarity to description and reword tests options

.github/pull_request_template.md

@@ -8,8 +8,11 @@ For more information on the requirements for pull requests, please see [the cont
     Add here detailed changes summary, testing results, dependencies
     Good example: https://os.mbed.com/docs/mbed-os/latest/contributing/workflow.html (Pull request template)
 -->
+##### Summary of change (*What the change is for and why*)
 
 
+##### Documentation (*Details of any document updates required*)
+
 ----------------------------------------------------------------------------------------------------------------
 ### Pull request type (*required*)
 
@@ -28,12 +31,12 @@ For more information on the requirements for pull requests, please see [the cont
 ### Test results (*required*)
 
 <!--
-    Optional
+    Required
     For example, add test results for new target
 -->
-    [] No Tests required for this change
+    [] No Tests required for this change (E.g docs only update)
-    [] These PR changes will be covered by existing tests and CI
+    [] Covered by existing mbed-os tests (Greentea or Unittest)
-    [] Tests supplied below
+    [] Tests / results supplied as part of this PR
     
     
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@@ -60,3 +63,4 @@ For more information on the requirements for pull requests, please see [the cont
 ##### Migration actions required
 
 
+