Add docs about browser extensions

docs/src/extensions.md

@@ -0,0 +1,11 @@
+# Browser Extensions
+
+Lapo Luchini has been kind enough to create extensions for both Chrome and
+Firefox. You can find his repo for these extensions at:
+
+- [https://github.com/lapo-luchini/chrome-pinry](https://github.com/lapo-luchini/chrome-pinry)
+
+If you'd like to install either extension they are available at:
+
+- [https://chrome.google.com/webstore/detail/pinry-chrome/pcbmmomiecgodaaffdgfeclomnjnmhin](https://chrome.google.com/webstore/detail/pinry-chrome/pcbmmomiecgodaaffdgfeclomnjnmhin)
+- [https://addons.mozilla.org/zh-CN/firefox/addon/pinry/](https://addons.mozilla.org/zh-CN/firefox/addon/pinry/)

mkdocs.yml

@@ -15,6 +15,7 @@ copyright: "Copyright © 2019 Pinry's Contributors"
 nav:
   - Home: 'index.md'
   - Screenshots: 'screenshots.md'
+  - Extensions: 'extensions.md'
   - Docs: 'docs.md'
   - Assets: 'assets.md'
   - Contributing: 'contributing.md'