openssl-genrsa: add page (#4050)

Co-authored-by: Zlatan Vasović <zlatanvasovic@gmail.com>
Co-authored-by: Ein Verne <git@einverne.info>
Co-authored-by: Starbeamrainbowlabs <sbrl@starbeamrainbowlabs.com>

pages/common/openssl-genrsa.md

@@ -0,0 +1,16 @@
+# openssl genrsa
+
+> OpenSSL command to generate RSA private keys.
+> More information: <https://www.openssl.org/docs/man1.0.2/man1/genrsa.html>.
+
+- Generate an RSA private key of 2048 bits to stdout:
+
+`openssl genrsa`
+
+- Save an RSA private key of an arbitrary number of bits to the output file:
+
+`openssl genrsa -out {{output_file.key}} {{1234}}`
+
+- Generate an RSA private key and encrypt it with AES256 (you will be prompted for a passphrase):
+
+`openssl genrsa {{-aes256}}`