Merge pull request 'Fix Doxygen warnings' (#29) from fix-doxygen-warnings into main

Doxyfile

@@ -7,10 +7,9 @@ PROJECT_NAME           = "Squirrel Census"
 PROJECT_BRIEF          = "Count squirrels by primary fur colour"
 PROJECT_NUMBER         = 0.1.0
 OUTPUT_DIRECTORY       = docs/doxygen
-INPUT                  = src README.md
+INPUT                  = src docs/mainpage.dox
-FILE_PATTERNS          = *.py *.md
+FILE_PATTERNS          = *.py *.dox
 RECURSIVE              = YES
-USE_MDFILE_AS_MAINPAGE = README.md
 OPTIMIZE_OUTPUT_JAVA   = YES
 EXTRACT_ALL            = YES
 GENERATE_HTML          = YES

docs/mainpage.dox

@@ -0,0 +1,13 @@
+/**
+@mainpage Squirrel Census
+
+Count the squirrels of the 2018 Central Park Squirrel Census by primary fur colour
+(Gray, Cinnamon, Black) and export the counts to `squirrel_count.csv`.
+
+The steps follow the Udemy "100 Days of Code" lecture of day 25: squirrel.census.read_csv,
+squirrel.census.count_by_fur_color, squirrel.census.build_summary and
+squirrel.census.write_csv. The command line entry point is squirrel.cli.main, started
+with `python -m squirrel`. Every literal is defined once in squirrel.constants.
+
+The package uses only the Python standard library.
+*/