Improve doc for NodePattern parameters [doc] [ci skip]

CHANGELOG.md

@@ -9,7 +9,7 @@
 * [#4](https://github.com/rubocop-hq/rubocop-ast/issues/4): Add `interpolation?` for `RegexpNode`. ([@tejasbubane][])
 * [#20](https://github.com/rubocop-hq/rubocop-ast/pull/20): Add option predicates for `RegexpNode`. ([@owst][])
 * [#11](https://github.com/rubocop-hq/rubocop-ast/issues/11): Add `argument_type?` method to make it easy to recognize argument nodes. ([@tejasbubane][])
-* [#31](https://github.com/rubocop-hq/rubocop-ast/pull/31): Use `param === node` to match params, which allows Regexp, Proc, Set, etc. ([@marcandre][])
+* [#31](https://github.com/rubocop-hq/rubocop-ast/pull/31): NodePattern now uses `param === node` to match params, which allows Regexp, Proc, Set in addition to Nodes and literals. ([@marcandre][])
 * [#41](https://github.com/rubocop-hq/rubocop-ast/pull/41): Add `delimiters` and related predicates for `RegexpNode`. ([@owst][])
 
 ## 0.0.3 (2020-05-15)

docs/modules/ROOT/pages/node_pattern.adoc

@@ -409,6 +409,10 @@ has_user_data?(node, /^pass(word)?$/i)
 has_user_data?(node, ->(key) { # return true or false depending on key })
 ----
 
+NOTE: `Array#===` will never match a single node element (so don't pass arrays),
+but `Set#===` is an alias to `Set#include?` (Ruby 2.5+ only), and so can be
+very useful to match within many possible literals / Nodes.
+
 == `nil` or `nil?`
 
 Take a special attention to nil behavior:

lib/rubocop/ast/node_pattern.rb

@@ -70,8 +70,12 @@ module AST
     #     '(send %1 _)'       # % stands for a parameter which must be supplied to
     #                         # #match at matching time
     #                         # it will be compared to the corresponding value in
-    #                         # the AST using #=== so you can pass Procs, Regexp
-    #                         # in addition to Nodes or literals.
+    #                         # the AST using #=== so you can pass Procs, Regexp,
+    #                         # etc. in addition to Nodes or literals.
+    #                         # `Array#===` will never match a node element, but
+    #                         # `Set#===` is an alias to `Set#include?` (Ruby 2.5+
+    #                         # only), and so can be very useful to match within
+    #                         # many possible literals / Nodes.
     #                         # a bare '%' is the same as '%1'
     #                         # the number of extra parameters passed to #match
     #                         # must equal the highest % value in the pattern