Add 9Slice schema (#184)

* Add 9Slice schema
* Add nineslice schema to vscode settings

source/resource/textures/nine_slice.json

@@ -0,0 +1,41 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema",
+  "$id": "blockception.minecraft.resource.texture.nine_slice",
+  "additionalProperties": false,
+  "description": "The file that specifies 9Slice textures.",
+  "title": "9Slice Texture File",
+  "type": "object",
+  "properties": {
+    "nineslice_size": {
+      "title": "9Slice offsets",
+      "oneOf": [
+        {
+          "description": "Offset from left, top, right and bottom of the texture file.",
+          "type": "number",
+          "minimum": 0
+        },
+        {
+          "description": "Offsets from left, top, right and bottom of the texture file (in this exact order).",
+          "type": "array",
+          "minItems": 4,
+          "maxItems": 4,
+          "items": {
+            "type": "number",
+            "minimum": 0
+          }
+        }
+      ]
+    },
+    "base_size": {
+      "title": "Size of the texture",
+      "description": "Width and height of the texture (in this exact order).",
+      "type": "array",
+      "minItems": 2,
+      "maxItems": 2,
+      "items": {
+        "type": "number",
+        "minimum": 0
+      }
+    }
+  }
+}