Automatically setup npm publish tag (graphql#1502)

Prevents issues similar to graphql#1375
See: https://docs.npmjs.com/files/package.json#publishconfig

resources/copy-package-json.js

@@ -11,8 +11,19 @@
  */
 
 const fs = require('fs');
+const assert = require('assert');
 
 const package = require('../package.json');
 delete package.scripts;
 delete package.devDependencies;
+
+const { version } = package;
+const match = /^[0-9]+\.[0-9]+\.[0-9]+-?([^.]*)/.exec(version);
+assert(match, 'Version does not match semver spec.');
+const tag = match[1];
+assert(!tag || tag === 'rc', 'Only "rc" tag is supported.');
+
+assert(!package.publishConfig, 'Can not override "publishConfig".');
+package.publishConfig = { tag: tag || 'latest' };
+
 fs.writeFileSync('./dist/package.json', JSON.stringify(package, null, 2));