Fix #5310: docs for unique[] filter operator (#5651)

Co-authored-by: clutterstack <clutterstack@gmail.com>

editions/tw5.com/tiddlers/filters/examples/unique Operator (Examples).tid

@@ -0,0 +1,8 @@
+created: 20210216203925301
+modified: 20210217003209935
+tags: [[unique Operator]] [[Operator Examples]]
+title: unique Operator (Examples)
+
+To remove duplicate entries from a list where deduplication has been prevented using the [[filter run prefix|Filter Expression]] `=`:
+
+<<.operator-example 1 """=[[E]] =[[A]] =[[B]] =[[C]] =[[C]] =[[D]] =[[C]] +[unique[]]""">>

editions/tw5.com/tiddlers/filters/unique.tid

@@ -0,0 +1,10 @@
+caption: unique
+op-input: a list of items
+op-output: a list of unique items
+op-parameter: ignored
+op-purpose: remove all duplicate items from the current list
+tags: [[Filter Operators]] [[Order Operators]] [[Listops Operators]]
+title: unique Operator
+type: text/vnd.tiddlywiki
+
+<<.operator-examples "unique">>