flat: convert steel-browser from submodule to regular folder

extensions/steel-browser/tsconfig.json

@@ -0,0 +1,22 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "module": "NodeNext",
+    "moduleResolution": "NodeNext",
+    "lib": ["ES2022", "DOM"],
+    "types": ["node"],
+    "strict": true,
+    "esModuleInterop": true,
+    "skipLibCheck": true,
+    "forceConsistentCasingInFileNames": true,
+    "isolatedModules": true,
+    "declaration": true,
+    "sourceMap": true,
+    "outDir": "dist",
+    "rootDir": "src",
+    "resolveJsonModule": true,
+    "noEmitOnError": true
+  },
+  "include": ["src/**/*.ts"],
+  "exclude": ["dist", "node_modules", "**/*.test.ts", "**/*.spec.ts"]
+}