fix: add prepare script for GitHub installations

Enables automatic building when installing from GitHub, ensuring dist directory with TypeScript declarations is generated

Author: cameroncooke

package.json

@@ -42,6 +42,7 @@
     "build:cjs": "mkdir -p dist/cjs && echo '{\"type\": \"commonjs\"}' > dist/cjs/package.json && tsc -p tsconfig.cjs.json",
     "build:cjs:w": "npm run build:cjs -- -w",
     "examples:simple-server:w": "tsx --watch src/examples/server/simpleStreamableHttp.ts --oauth",
+    "prepare": "npm run build",
     "prepack": "npm run build:esm && npm run build:cjs",
     "lint": "eslint src/",
     "test": "npm run fetch:spec-types && jest",