[DOC] Cookbook and Changelog

Co-authored-by: Enrico Seiler <enrico.seiler@hotmail.de>

CHANGELOG.md

@@ -32,6 +32,7 @@ If possible, provide tooling that performs the changes, e.g. a shell-script.
   * `seqan3::cigar` can now be assigned from `std::string_view` ([\#2966](https://github.com/seqan/seqan3/pull/2966)).
   * Added `seqan3::views::char_strictly_to`. Behaves like `seqan3::views::char_to`, but throws on invalid
     input ([\#2898](https://github.com/seqan/seqan3/pull/2898)).
+  * Improved performance of `seqan3::dna4::complement()` ([\#3026](https://github.com/seqan/seqan3/pull/3026)).
 
 #### I/O
  * Added `seqan3::sequence_file_option::fasta_ignore_blanks_before_id` to ignore blanks before IDs when reading FASTA

doc/cookbook/index.md

@@ -198,3 +198,14 @@ This will use `4` threads by default and can be adjusted by setting `seqan3::con
 the desired value:
 
 \snippet doc/cookbook/compression_threads.cpp example
+
+# Auto vectorized dna4 complement
+
+Our alphabet seqan3::dna4 cannot be easily auto-vectorized by the compiler.
+
+See [this discussion](https://github.com/seqan/seqan3/issues/1970) for more details.
+
+You can add your own alphabet that is auto-vectorizable in some use cases.
+Here is an example for a dna4-like alphabet:
+
+\snippet test/performance/simd_dna4.hpp cookbook

doc/cookbook/simd_dna4.cpp

@@ -0,0 +1,9 @@
+// Checks that defining simd_dna4 works without putting it into the seqan3 namespace.
+
+#define SEQAN3_USE_NAMESPACE 0
+#include <seqan3/test/performance/simd_dna4.hpp>
+
+int main()
+{
+    simd_dna4 [[maybe_unused]] letter{};
+}