Add OpenSSL-related file extensions (#3168)

There are a number of OpenSSL-related file extensions (e.g., .pem, .crt,
etc..) that contain data that are generally best not committed to
repositories.  This file contains several common file extensions that
often correlate to these types of files.

community/OpenSSL.gitignore

+# OpenSSL-related files best not committed
+
+## Certificate Authority
+*.ca
+
+## Certificate
+*.crt
+
+## Certificate Sign Request
+*.csr
+
+## Certificate
+*.der 
+
+## Key database file
+*.kdb
+
+## OSCP request data
+*.org
+
+## PKCS #12
+*.p12
+
+## PEM-encoded certificate data
+*.pem
+
+## Random number seed
+*.rnd
+
+## SSLeay data
+*.ssleay
+
+## S/MIME message
+*.smime