Add v0.1 scaffold: tree-sitter-p8-cart grammar and Zed extension

The grammar parses the .p8 cartridge container ( header, version, and
the named __lua__/__gfx__/__gff__/__label__/__map__/__sfx__/__music__
sections, plus a fallback unknown_section ). The Zed language definition
hands the __lua__ body to Zed's built-in Lua via injections.scm, so
non-dialect Lua code highlights correctly today; PICO-8-specific syntax
(?, +=, !=, single-line if, etc.) will fall back to error highlighting
in those regions only — see README roadmap for the dialect grammar fork.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tree-sitter.json

@@ -0,0 +1,29 @@
+{
+  "grammars": [
+    {
+      "name": "p8-cart",
+      "camelcase": "P8Cart",
+      "scope": "source.p8-cart",
+      "path": ".",
+      "file-types": [
+        "p8"
+      ]
+    }
+  ],
+  "metadata": {
+    "version": "0.0.1",
+    "license": "0BSD",
+    "description": "tree-sitter grammar for the PICO-8 .p8 cartridge text format",
+    "links": {
+      "repository": "https://github.com/tree-sitter/tree-sitter-p8-cart"
+    }
+  },
+  "bindings": {
+    "c": true,
+    "go": true,
+    "node": true,
+    "python": true,
+    "rust": true,
+    "swift": true
+  }
+}