Merge pull request #421 from MeVitae/doxygen-docs

Doxygen docs

.gitignore

@@ -245,3 +245,5 @@ _Pvt_Extensions
 /src/test-results.xml
 /tools/benchmark
 /tools/ConsoleRunner/Properties/launchSettings.json
+
+/docs/doxygen

README.md

@@ -299,6 +299,10 @@ You can merge 2 or more existing PDF files using the `PdfMerger` class:
     var resultFileBytes = PdfMerger.Merge(filePath1, filePath2);
     File.WriteAllBytes(@"C:\pdfs\outputfilename.pdf", resultFileBytes);
 
+## API Reference
+
+If you wish to generate doxygen documentation, run `doxygen doxygen-docs` and open `docs/doxygen/html/index.html`.
+
 ## Issues
 
 Please do file an issue if you encounter a bug.