Add missing docs for COLLECT (#605) (#606)

These parts existed for EXISTS and COUNT, but not for COLLECT.

---------
Cherry-picked from #605

Co-authored-by: Louise Söderström <[email protected]>

Author: renetapopova

modules/ROOT/pages/keyword-glossary.adoc

@@ -1015,15 +1015,17 @@ xref::functions/temporal/index.adoc#functions-temporal-truncate-overview[Truncat
 |===
 | Name | Description
 
-| xref::syntax/expressions.adoc#query-syntax-case[CASE Expression]
+| xref::syntax/expressions.adoc#query-syntax-case[CASE]
 | A generic conditional expression, similar to if/else statements available in other languages.
 
-| xref:syntax/expressions.adoc#existential-subqueries[EXISTS {...}]
-| An `EXISTS` expression is used to evaluate the existence of a subquery.
+| xref:syntax/expressions.adoc#collect-subqueries[COLLECT {...}]
+| Creates a list with the rows returned by a subquery.
 
 | xref:syntax/expressions.adoc#count-subqueries[COUNT {...}]
-| An expression used to compute the number of results of a subquery.
+| Computes the number of results of a subquery.
 
+| xref:syntax/expressions.adoc#existential-subqueries[EXISTS {...}]
+| Evaluates the existence of a subquery.
 |===
 
 

modules/ROOT/pages/syntax/index.adoc

@@ -14,6 +14,7 @@
  ** xref::syntax/expressions.adoc#cypher-subquery-expressions[Subquery expressions]
  *** xref::syntax/expressions.adoc#existential-subqueries[`EXISTS` subqueries]
  *** xref::syntax/expressions.adoc#count-subqueries[`COUNT` subqueries]
+ *** xref::syntax/expressions.adoc#collect-subqueries[`COLLECT` subqueries]
  ** xref::syntax/expressions.adoc#label-expressions[Label expressions]
  ** xref::syntax/expressions.adoc#relationship-type-expressions[Relationship type expressions]
 * xref::syntax/variables.adoc[Variables]