Include Rider as a supported IDE (#3323)

AS far as I can tell this .gitignore also applies to Rider. Looking at the somewhat official .gitignore for Rider [here](https://github.com/JetBrains/resharper-rider-samples/blob/master/.gitignore), it seems compatible.

Global/JetBrains.gitignore

@@ -1,4 +1,4 @@
-# Covers JetBrains IDEs: IntelliJ, RubyMine, PhpStorm, AppCode, PyCharm, CLion, Android Studio and WebStorm
+# Covers JetBrains IDEs: IntelliJ, RubyMine, PhpStorm, AppCode, PyCharm, CLion, Android Studio, WebStorm and Rider
 # Reference: https://intellij-support.jetbrains.com/hc/en-us/articles/206544839
 
 # User-specific stuff