Fixed typo in `CSP_DEFAULT_SRC` variable
`CS_DEFAULT_SRC` to `CSP_DEFAULT_SRC`; according to
@@ -14,4 +14,4 @@ CSP_SCRIPT_SRC = ("'self'",)
CSP_IMG_SRC = ("'self'",)
CSP_FONT_SRC = ("'self'",)
CSP_STYLE_SRC = ("'self'",)
-CS_DEFAULT_SRC = ("'none'",)
+CSP_DEFAULT_SRC = ("'none'",)
