Add cheatsheet for gem

gem

@@ -0,0 +1,29 @@
+---
+tags: [ packaging ]
+---
+# To search for a package:
+gem search <package>
+
+# To install packages:
+gem install <package>
+
+# To install a package in user space:
+gem install --user-install <package>
+
+# To install specific version of a package:
+gem install <package> -v <version>
+
+# To uninstall packages:
+gem uninstall <package>
+
+# To upgrade a package:
+gem update <package>
+
+# To show details of a package:
+gem info <package>
+
+# To list local packages:
+gem list --local
+
+# To show help on command
+gem help <command>