Integrate Markdoc library with Keystatic CMS.

The commit introduces the '@markdoc/markdoc' library to the Keystatic CMS. It modifies related functions and components such as 'KeystaticDocumentRenderer' and 'keystatic-client' to transform and render content using Markdoc. Additionally, the commit refactors 'keystatic.config.ts' file for more legible content field setup and adds related dependencies in the package.

packages/cms/keystatic/package.json

@@ -16,7 +16,8 @@
   },
   "dependencies": {
     "@keystatic/core": "0.5.14",
-    "@keystatic/next": "5.0.0"
+    "@keystatic/next": "5.0.0",
+    "@markdoc/markdoc": "^0.4.0"
   },
   "devDependencies": {
     "@kit/cms": "workspace:^",
@@ -25,6 +26,8 @@
     "@kit/tsconfig": "workspace:*",
     "@kit/ui": "workspace:^",
     "@types/node": "^20.12.8",
+    "@types/react": "^18.3.1",
+    "react": "18.3.1",
     "zod": "^3.23.6"
   },
   "eslintConfig": {