Add missing initializer_list constructors to reference docs

doc/unordered/unordered_set.adoc

@@ -67,6 +67,9 @@ namespace boost {
     template<class InputIterator>
       xref:#unordered_set_iterator_range_constructor_with_bucket_count_and_hasher[unordered_set](InputIterator f, InputIterator l, size_type n, const hasher& hf,
                     const allocator_type& a);
+    xref:#unordered_set_initializer_list_constructor_with_bucket_count_and_allocator[unordered_set](std::initializer_list<value_type> il, size_type n, const allocator_type& a);
+    xref:#unordered_set_initializer_list_constructor_with_bucket_count_and_hasher_and_allocator[unordered_set](std::initializer_list<value_type> il, size_type n, const hasher& hf,
+                  const allocator_type& a);
     xref:#unordered_set_destructor[~unordered_set]();
     unordered_set& xref:#unordered_set_copy_assignment[operator++=++](const unordered_set& other);
     unordered_set& xref:#unordered_set_move_assignment[operator++=++](unordered_set&& other)
@@ -520,6 +523,33 @@ Requires:;; `key_equal` needs to be https://en.cppreference.com/w/cpp/named_req/
 
 ---
 
+==== initializer_list Constructor with Bucket Count and Allocator
+
+```c++
+unordered_set(std::initializer_list<value_type> il, size_type n, const allocator_type& a);
+```
+
+Constructs an empty container with at least `n` buckets, using `a` as the allocator and a maximum load factor of 1.0 and inserts the elements from `il` into it.
+
+[horizontal]
+Requires:;; `hasher` and `key_equal` need to be https://en.cppreference.com/w/cpp/named_req/DefaultConstructible[DefaultConstructible^].
+
+---
+
+==== initializer_list Constructor with Bucket Count and Hasher and Allocator
+
+```c++
+unordered_set(std::initializer_list<value_type> il, size_type n, const hasher& hf,
+              const allocator_type& a);
+```
+
+Constructs an empty container with at least `n` buckets, using `hf` as the hash function, `a` as the allocator and a maximum load factor of 1.0 and inserts the elements from `il` into it.
+
+[horizontal]
+Requires:;; `key_equal` needs to be https://en.cppreference.com/w/cpp/named_req/DefaultConstructible[DefaultConstructible^].
+
+---
+
 === Destructor
 
 ```c++