Add more documentation for the following:

- what the `gh-cache` branch is for
- PDF scanning is outside our scope

Author: JoyceZhu

FAQ.md

@@ -0,0 +1,31 @@
+# [Frequently-Asked Questions (FAQ)]
+
+## `find` Action (Scanning for problems)
+
+### Do you support scanning PDFs?
+
+We're focusing this Action on website accessibility and currently don't plan to
+add PDF scanning capabilities.
+
+If you're looking to scan PDFs, we recommend using one of the
+[standalone PDF accessibility checkers listed by the PDF
+Association](https://pdfa.org/tools-for-accessible-pdf/).
+
+## Other / repository-wide questions
+
+### What is the `gh-cache` branch/Action for?
+
+Short answer: This is an orphan branch for storing information between Actions
+runs. It's an implementation detail and can be safely ignored by users.
+
+Longer answer: We use the `gh-cache` branch and [its associated
+Action](https://github.com/github/accessibility-scanner/tree/066e45c819d270bfb2392cfe141b570131c8011b/.github/actions/gh-cache)
+to persist issue data between action runs, which both prevents opening duplicate
+issues and allows us to automatically close issues which have been fixed
+(in other words, if a problem wasn't detected again in an ensuing run, it is
+therefore no longer a problem).
+
+Using a `git` branch as a caching mechanism allows users to view and/or edit the current
+contents of the cache through the usual GitHub user interface. It also means the
+contents of the cache are version controlled and can be changed through the
+`git` commands users are accustomed to.

README.md

@@ -4,7 +4,7 @@ The AI-powered Accessibility Scanner (a11y scanner) is a GitHub Action that dete
 
 The a11y scanner helps teams:
 
-- 🔍 Scan websites, files, repositories, and dynamic content for accessibility issues
+- 🔍 Scan websites, repositories, and dynamic content for accessibility issues
 - 📝 Create actionable GitHub issues that can be assigned to GitHub Copilot
 - 🤖 Propose fixes with GitHub Copilot, with humans reviewing before merging
 
@@ -14,6 +14,8 @@ The a11y scanner helps teams:
 
 ---
 
+## [Frequently-Asked Questions (FAQ)](FAQ.md)
+
 ## Requirements
 
 To use the a11y scanner, you'll need:
@@ -148,11 +150,11 @@ The a11y scanner leverages GitHub Copilot coding agent, which can be configured
 
 💬 We welcome your feedback! To submit feedback or report issues, please create an issue in this repository. For more information on contributing, please refer to the [CONTRIBUTING](./CONTRIBUTING.md) file.
 
-## License 
+## License
 
 📄 This project is licensed under the terms of the MIT open source license. Please refer to the [LICENSE](./LICENSE) file for the full terms.
 
-## Maintainers 
+## Maintainers
 
 🔧 Please refer to the [CODEOWNERS](./.github/CODEOWNERS) file for more information.