DOC-525 | Add more context to headlines in the AQL book (#1456)

* Add more context to headlines in the AQL book

Add some lead paragraphs

Combine UDF pages and integrate array operators

* Fix links, add another cross-reference

* Apply to 3.11

* Apply to 3.10

Author: Simran-B

3.10/aql/advanced-array-operators.md

@@ -1,11 +1,15 @@
 ---
 layout: default
-description: Common errors to make in ArangoDB's query language
-title: AQL Pitfalls
+description: >-
+  Avoid injection vulnerabilities and avoid pitfalls like incorrect operator
+  usage performance issues when using ArangoDB's query language
 ---
-Common Errors
+Common Errors in AQL
 =============
 
+{{ page.description }}
+{:class="lead"}
+
 Trailing semicolons in query strings
 ------------------------------------