Update documentation for reports, new CLI

This is basically a redraft of the documentation to be more complete and
better cover some of the features added since it was written.

docs/src/debugging.md

@@ -0,0 +1,9 @@
+# Debugging
+
+Both `task` and `taskchampion-sync-server` use [env-logger](https://docs.rs/env_logger) and can be configured to log at various levels with the `RUST_LOG` environment variable.
+For example:
+```shell
+$ RUST_LOG=taskchampion=trace task add foo
+```
+
+The output may provide valuable clues in debugging problems.