Add collection querying rule

Author: lovro-bikic

README.adoc

@@ -4690,6 +4690,31 @@ ary[..42]
 ary[0..42]
 ----
 
+=== Collection querying [[collection-querying]]
+
+When possible, use https://docs.ruby-lang.org/en/master/Enumerable.html#module-Enumerable-label-Methods+for+Querying[predicate methods from `Enumerable`] rather than expressions with `#count`.
+
+[source,ruby]
+----
+# bad
+array.count > 0
+array.count(&:something).positive?
+
+array.count == 0
+
+array.count == 1
+
+# good
+array.any?
+array.any?(&:something)
+
+array.none?
+
+array.one?
+----
+
+NOTE: Predicate methods aren't applicable when collection includes falsy values (e.g. `[nil].one?` evaluates to `false`).
+
 == Numbers
 
 === Underscores in Numerics [[underscores-in-numerics]]