Read GitHub personal access token from ~/.netrc.

Reference: https://github.com/jekyll/github-metadata/blob/master/docs/authentication.md#2-netrc

Signed-off-by: Mark Lodato <lodato@google.com>

docs/Gemfile

 source "https://rubygems.org"
 gem 'github-pages', group: :jekyll_plugins
+gem 'netrc'

docs/Gemfile.lock

@@ -233,6 +233,7 @@ GEM
       jekyll-seo-tag (~> 2.1)
     minitest (5.15.0)
     multipart-post (2.1.1)
+    netrc (0.11.0)
     nokogiri (1.13.0)
       mini_portile2 (~> 2.7.0)
       racc (~> 1.4)
@@ -281,6 +282,7 @@ PLATFORMS
 
 DEPENDENCIES
   github-pages
+  netrc
 
 BUNDLED WITH
    2.1.4

docs/README.md

@@ -28,14 +28,24 @@ via GitHub pages and rendered with Jekyll.
     bundle install
     ```
 
-4.  Run the project locally with `jekyll serve` (optionally appending
+4.  (optional) Create a GitHub
+    [personal access token](https://github.com/settings/tokens/new) and add it
+    to your `~/.netrc`, like so:
+
+    ```none
+    machine api.github.com
+        login github-username
+        password 123abc-your-token
+    ```
+
+5.  Run the project locally with `jekyll serve` (optionally appending
     `--livereload`):
 
     ```bash
     bundle exec jekyll serve
     ```
 
-5.  Browse to http://localhost:4000 to view the site locally.
+6.  Browse to http://localhost:4000 to view the site locally.
 
 ## Deployment