Updated local setup steps.

Author: ashryanbeats

CONTRIBUTING.md

@@ -18,8 +18,8 @@ consensus around project direction and issue solutions within issue threads
 
 Please note the following:
 
-* Pull Requests to the plugin-docs repository will be rejected; please file an issue for incorrect documentation instead. This is because we need to ensure that the issue is corrected in the internal source code.
-* Pull Requests to the plugin-samples repository and other repositories in the AdobeXD organization are welcome. Please file an issue first so that your contribution can be discussed.
+- Pull Requests to the plugin-docs repository will be rejected; please file an issue for incorrect documentation instead. This is because we need to ensure that the issue is corrected in the internal source code.
+- Pull Requests to the plugin-samples repository and other repositories in the AdobeXD organization are welcome. Please file an issue first so that your contribution can be discussed.
 
 ## Contributor License Agreement
 
@@ -35,6 +35,8 @@ Security issues shouldn't be reported on this issue tracker. Instead, [file an i
 
 ## Viewing Docs Locally
 
+### Setup
+
 To preview the fully formatted docs as they will appear online, follow these steps:
 
 ```bash
@@ -51,4 +53,39 @@ python -m SimpleHTTPServer 8000
 # ...then open http://localhost:8000
 ```
 
-Testing this way is important since formatting that looks fine in your Markdown viewer of choice may be interpreted differently by Gitbook's HTML generator.
+### Preparing to push changes
+
+When you're done making changes:
+
+```bash
+# Rebuild HTML content
+npm run book:build
+
+# Check for 404s
+npm run test:404 # See notes below about this
+
+# Push to GitHub
+git push
+```
+
+From there, submit your pull request.
+
+### Checking for 404s locally
+
+When you run `npm run book:build`, you'll wait for a bit as the script scans the site, and then get a report of any found 404s in your terminal. Detailed logs will be dumped to `./.logs/log.txt`.
+
+Generally you can safely ignore these 404s:
+
+- `/plugin-docs/images/xd-logo.png` (due to the way the repo is structured, this image will only appear on the published site)
+- `console.adobe.io` links (because the script isn't logged in, it gets a 404 from the Console)
+- `ngrok` links (used in code samples; not expected to function as links)
+
+### Publishing
+
+If you're an Adobe person, when you're ready to publish the changes, run:
+
+```bash
+npm run book:publish:github
+```
+
+The changes will appear in bit!