Introduce KORAPXMLTEI_DEBUG and document environment variables

Change-Id: I2d6232e475ea059ac1afee92a7fb088a39f61e7e
diff --git a/Readme.pod b/Readme.pod
index a71f3c8..d3cca5b 100644
--- a/Readme.pod
+++ b/Readme.pod
@@ -122,6 +122,22 @@
 
 =back
 
+=head1 ENVIRONMENT VARIABLES
+
+=over 2
+
+=item B<KORAPXMLTEI_DEBUG>
+
+Activate minimal debugging.
+Defaults to C<false>.
+
+=item B<KORAPXMLTEI_INLINE>
+
+Process inline annotations, if present.
+Defaults to C<false>.
+
+=back
+
 =head1 COPYRIGHT AND LICENSE
 
 Copyright (C) 2020, L<IDS Mannheim|https://www.ids-mannheim.de/>