Update README

README.md

@@ -1,17 +1,20 @@
 # Doxygen Docker Action
-This [GitHub Action](https://github.com/features/actions) will build [doxygen](http://doxygen.nl/) docs according to a specified Doxyfile - if omitted will search in the root directory of the repo.
+This [GitHub Action](https://github.com/features/actions) will build [doxygen](http://doxygen.nl/) docs from the specified doxyfile.
 
 Use with an action such as [actions-gh-pages](https://github.com/peaceiris/actions-gh-pages) to deploy to your project's GitHub pages site!
 
 **NOTE:** If you are using dot/graphviz in your doxygen config to generate diagrams the only fonts installed, and hence can be used are those in the [GNU FreeFont](https://www.gnu.org/software/freefont/) package (FreeSans, FreeMono and FreeSerif).
 
 ## Inputs
+### 'working-directory'
+**Required** Path of the working directory to change to before running doxygen. Default: `.`
 ### 'doxyfile-path'
-**Required** Path of the Doxyfile relative to the repository root. Default: `./Doxyfile`.
+**Required** Path of the Doxyfile relative to the working directory. Default: `./Doxyfile`.
 
 ## Example usage
 ```yaml
 uses: mattnotmitt/doxygen-action@v1
 with:
+    working-directory: 'submodule/'
     doxyfile-path: 'docs/Doxygen'
-```
+```