Add Slovak language (#143)

* Create sk

Hi, I'm minecraft translator for slovak language. i have seen this project and i will use it mainly for dimensions generating. from my experience if it is on github then it is translatable (not really but mostly)... so i got into here and translated this

-Name: Slovenčina
-mc namespace: sk_SK
-short: SK
-in english: Slovak (language)

src/config.json

@@ -32,6 +32,10 @@
       "code": "ru",
       "name": "Русский"
     },
+    {
+      "code": "sk",
+      "name": "Slovenčina"
+    },
     {
       "code": "zh-cn",
       "name": "简体中文"