Add blank line before list after paragaph

So that it is displayed correctly as list in ReadTheDocs

Author: shaedrich

docs/topics/defined-names.md

@@ -545,6 +545,7 @@ $this->spreadsheet->addDefinedName(
 ### Naming Names
 
 The names that you assign to Defined Name must follow the following set of rules:
+
  - The first character of a name must be one of the following characters:
    - letter (including UTF-8 letters)
    - underscore (`_`)