fix: copy the readme and license files in the dist folder so that the readme is available directly on NPM and the license as well

Author: maxime1992

package.json

@@ -7,7 +7,7 @@
   "types": "dist/types.d.ts",
   "scripts": {
     "tsc": "tsc",
-    "build": "rm -rf dist && yarn tsc && cp src/package.json dist"
+    "build": "rm -rf dist && yarn tsc && cp src/package.json dist && cp README.md dist && cp LICENSE.md dist"
   },
   "dependencies": {
     "@improbable-eng/grpc-web": "0.15.0",