compat: Chipped & Eternal Starlight

TODO: Frosted Leaves and Northland Leaves need new snowy models with top and bottom textures. Perhaps I could change the default model to have bottom and top texture variables that by default take on the regular side texture.

input/assets/eternal_starlight/textures/block/northland_leaves.betterleaves.json

@@ -0,0 +1,6 @@
+{
+    "blockStateData": {
+        "block": "eternal_starlight:northland_leaves",
+        "state": "snowy=false"
+    }
+}

input/assets/eternal_starlight/textures/block/northland_leaves_snowy.betterleaves.json

@@ -0,0 +1,10 @@
+{
+    "blockStateData": {
+        "block": "eternal_starlight:northland_leaves",
+        "state": "snowy=true"
+    },
+    "textureStitching": {
+        "1-3": "minecraft:block/snow",
+        "7-9": "eternal_starlight:block/northland_leaves"
+    }
+}