Add .editorconfig entry for .rst files to enforce space indentation

.editorconfig

@@ -21,6 +21,9 @@ indent_style = space
 [*.yml]
 indent_style = space
 
+[*.rst]
+indent_style = space
+
 # Tests don't get a line width restriction.  It's still a good idea to follow
 # the 79 character rule, but in the interests of clarity, tests often need to
 # violate it.