feat: support pure css modules (#1008)

Author: evilebottnawi

README.md

@@ -317,6 +317,7 @@ module.exports = {
 
 Using `local` value requires you to specify `:global` classes.
 Using `global` value requires you to specify `:local` classes.
+Using `pure` value requires selectors must contain at least one local class or id.
 
 You can find more information [here](https://github.com/css-modules/css-modules).
 

src/options.json

@@ -30,14 +30,14 @@
           "type": "boolean"
         },
         {
-          "enum": ["local", "global"]
+          "enum": ["local", "global", "pure"]
         },
         {
           "type": "object",
           "additionalProperties": false,
           "properties": {
             "mode": {
-              "enum": ["local", "global"]
+              "enum": ["local", "global", "pure"]
             },
             "localIdentName": {
               "type": "string"