Rename CMS-specific labeling to "platform" in add-site docs (#47)

Part of ENG-3134. The "All CMS" filter is being renamed to "All
Platforms" across the SaaS app as scope expands beyond CMS platforms
(npm, vibe-coded tools). Update docs.patchstack.com accordingly: the
add-site step described "choose your CMS", but the app dialog already
labels this selection "Platform". Reword the docs to match the live UI
and the broader platform concept.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: mariojgt

src/content/docs/Patchstack App/Sites/adding-a-site.mdx

@@ -16,9 +16,9 @@ Adding a site to Patchstack is relatively easy. Here is a simple guide on how to
 <Steps>
 1. Navigate to the <a href="https://app.patchstack.com/sites" target="_blank">**Sites**</a> view in Patchstack App
 2. Click on **+ Add new** button. ![](@images/patchstack-sites-add-new.png)
-3. Type your domain name into the popup and choose your CMS: ![](@images/patchstack-add-first-site-dialogue.png)
+3. Type your domain name into the popup and choose your platform: ![](@images/patchstack-add-first-site-dialogue.png)
 4. Click on **Continue to plugin/connector sync**.  
-5. In case you chose WordPress, continue with the steps below. If you chose other CMS, check  <a href="/patchstack-plugin/patchstack-connector/how-to-install-on-drupal/" target="_blank"><b>Drupal instructions</b></a>
+5. In case you chose WordPress, continue with the steps below. If you chose a different platform, check  <a href="/patchstack-plugin/patchstack-connector/how-to-install-on-drupal/" target="_blank"><b>Drupal instructions</b></a>
 6. You will be taken to the next step, where you can follow the next instructions.  ![](@images/patchstack-checking-sync-status.png)
 7. Click **Download latest plugin**
 8. Upload the plugin .zip file to your WordPress site by visiting /wp-admin > Plugins > Add New > Upload Plugin