Enable tree-shaking (#76)

Author: timostamm

packages/bench-codesize/README.md

@@ -9,5 +9,5 @@ minify the bundle, and compress it like a web server would usually do.
 
 | code generator    | bundle size             | minified               | compressed         |
 |-------------------|------------------------:|-----------------------:|-------------------:|
-| protobuf-es       | 160,619 b      | 86,421 b | 15,098 b |
+| protobuf-es       | 72,457 b      | 35,936 b | 9,393 b |
 | google-protobuf   | 368,034 b  | 270,748 b | 43,704 b |

packages/protobuf/package.json

@@ -8,6 +8,7 @@
     "url": "https://github.com/bufbuild/protobuf-es.git",
     "directory": "packages/protobuf"
   },
+  "sideEffects": false,
   "scripts": {
     "clean": "rm -rf ./dist/cjs/* ./dist/esm/* ./dist/types/*",
     "build": "npm run build:cjs && npm run build:esm+types",