chore: add typecheck command (#6140)

If you want to run TypeScript only to verify that it's typechecking correctly, this command is quicker as it doesn't output CJS and ESM to disk. Useful for checking during development.

package.json

@@ -27,6 +27,7 @@
     "tsc": "npm run clean-lib && tsc --version && npm run tsc-cjs && npm run tsc-esm",
     "tsc-cjs": "tsc -p . && cp src/protocol.d.ts lib/cjs",
     "tsc-esm": "tsc --build tsconfig-esm.json && cp src/protocol.d.ts lib/esm",
+    "typecheck": "tsc -p . --noEmit",
     "apply-next-version": "node utils/apply_next_version.js",
     "update-protocol-d-ts": "node utils/protocol-types-generator update",
     "compare-protocol-d-ts": "node utils/protocol-types-generator compare",