feat: generate JSON schemas for all manifest versions

Updated build script to generate JSON schemas for all historical manifest
versions (v0.1, v0.2, v0.3) in addition to the latest version.

Changes:
- Generate mcpb-manifest-v0.1.schema.json
- Generate mcpb-manifest-v0.2.schema.json
- Generate mcpb-manifest-v0.3.schema.json
- Generate mcpb-manifest-latest.schema.json
- Keep mcpb-manifest.schema.json as alias for latest
- All schemas generated to both dist/ and schemas/ directories
- Added exports in package.json for all versioned schemas

Benefits:
- Tools can validate against specific manifest versions
- Backwards compatibility for all historical versions
- Latest schema always available at predictable path
- JSON schema files match the Zod schema versions

Usage:
import manifestSchema from '@anthropic-ai/mcpb/mcpb-manifest-v0.2.schema.json'
import latestSchema from '@anthropic-ai/mcpb/mcpb-manifest-latest.schema.json'

schemas/mcpb-manifest.schema.json

@@ -6,12 +6,12 @@
     },
     "dxt_version": {
       "type": "string",
-      "const": "0.2",
+      "const": "0.3",
       "description": "@deprecated Use manifest_version instead"
     },
     "manifest_version": {
       "type": "string",
-      "const": "0.2"
+      "const": "0.3"
     },
     "name": {
       "type": "string"
@@ -80,12 +80,54 @@
     "icon": {
       "type": "string"
     },
+    "icons": {
+      "type": "array",
+      "items": {
+        "type": "object",
+        "properties": {
+          "src": {
+            "type": "string"
+          },
+          "sizes": {
+            "type": "string",
+            "pattern": "^\\d+x\\d+$"
+          },
+          "theme": {
+            "type": "string",
+            "minLength": 1
+          }
+        },
+        "required": [
+          "src",
+          "sizes"
+        ],
+        "additionalProperties": false
+      }
+    },
     "screenshots": {
       "type": "array",
       "items": {
         "type": "string"
       }
     },
+    "localization": {
+      "type": "object",
+      "properties": {
+        "resources": {
+          "type": "string",
+          "pattern": "\\$\\{locale\\}"
+        },
+        "default_locale": {
+          "type": "string",
+          "pattern": "^[A-Za-z0-9]{2,8}(?:-[A-Za-z0-9]{1,8})*$"
+        }
+      },
+      "required": [
+        "resources",
+        "default_locale"
+      ],
+      "additionalProperties": false
+    },
     "server": {
       "type": "object",
       "properties": {
@@ -313,6 +355,13 @@
         ],
         "additionalProperties": false
       }
+    },
+    "_meta": {
+      "type": "object",
+      "additionalProperties": {
+        "type": "object",
+        "additionalProperties": {}
+      }
     }
   },
   "required": [