Add auth support (#21)

* Updates

* Update

* Update

* Update

* Update

* Yarn sometimes prefers npmrc, so use same token

* Description

* Update readme

* Feedback

* Add type

* new toolkit and scoped registries

* npmrc in RUNNER_TEMP

* Dont always auth

* Try exporting blank token

* Get auth working for now pending runner changes

* Fix string interpolation for auth token.

* Don't export both userconfigs

* Update authutil.js

* Add single quotes for authString

* Fix the registry string.

* Use userconfig and append trailing slash

* Keep in root of repo

* Try just adding auth token

* Remove auth token

* Try changes again

* Add tests

* Npm and GPR samples

* Add types

node_modules/universal-user-agent/index.js

@@ -0,0 +1,15 @@
+module.exports = getUserAgentNode
+
+const osName = require('os-name')
+
+function getUserAgentNode () {
+  try {
+    return `Node.js/${process.version.substr(1)} (${osName()}; ${process.arch})`
+  } catch (error) {
+    if (/wmic os get Caption/.test(error.message)) {
+      return 'Windows <version undetectable>'
+    }
+
+    throw error
+  }
+}