🎨 Annotate bits of pytest config

In particular, this patch adds a link to the doctest documentation
page and describes the `norecursedirs` optimization.

Author: webknjaz

pytest.ini

@@ -20,6 +20,7 @@ addopts =
   --showlocals
 
   # Autocollect and invoke the doctests from all modules:
+  # https://docs.pytest.org/en/stable/doctest.html
   --doctest-modules
 
   # Dump the test results in junit format:
@@ -37,6 +38,7 @@ junit_duration_report = call
 junit_family = xunit2
 junit_suite_name = magicbus_test_suite
 minversion = 4.6.9
+# Optimize pytest's lookup by restricting potentially deep dir tree scan:
 norecursedirs =
   build
   magicbus.egg-info