doc: add documentation for createDiffieHellmanGroup

doc/api/crypto.md

@@ -1733,6 +1733,13 @@ Creates a `DiffieHellman` key exchange object and generates a prime of
 `primeLength` bits using an optional specific numeric `generator`.
 If `generator` is not specified, the value `2` is used.
 
+### crypto.createDiffieHellmanGroup()
+<!-- YAML
+added: v12.6.0
+-->
+
+An alias for [`crypto.getDiffieHellman()`][]
+
 ### crypto.createECDH(curveName)
 <!-- YAML
 added: v0.11.14
@@ -3226,6 +3233,7 @@ the `crypto`, `tls`, and `https` modules and are generally specific to OpenSSL.
 [`crypto.createSign()`]: #crypto_crypto_createsign_algorithm_options
 [`crypto.createVerify()`]: #crypto_crypto_createverify_algorithm_options
 [`crypto.getCurves()`]: #crypto_crypto_getcurves
+[`crypto.getDiffieHellman()`]: #crypto_crypto_getdiffiehellman
 [`crypto.getHashes()`]: #crypto_crypto_gethashes
 [`crypto.privateDecrypt()`]: #crypto_crypto_privatedecrypt_privatekey_buffer
 [`crypto.privateEncrypt()`]: #crypto_crypto_privateencrypt_privatekey_buffer