docs: add docs for wutta export-csv command

docs/api/wuttasync.cli.export_csv.rst

@@ -0,0 +1,6 @@
+
+``wuttasync.cli.export_csv``
+============================
+
+.. automodule:: wuttasync.cli.export_csv
+   :members:

docs/index.rst

@@ -73,6 +73,7 @@ cf. :doc:`rattail-manual:data/sync/index`.
    api/wuttasync.app
    api/wuttasync.cli
    api/wuttasync.cli.base
+   api/wuttasync.cli.export_csv
    api/wuttasync.cli.import_csv
    api/wuttasync.cli.import_versions
    api/wuttasync.emails

docs/narr/cli/builtin.rst

@@ -9,6 +9,24 @@ WuttaSync.
 It is fairly simple to add more; see :doc:`custom`.
 
 
+.. _wutta-export-csv:
+
+``wutta export-csv``
+--------------------
+
+Export data from the Wutta :term:`app database` to CSV file(s).
+
+This *should* be able to automatically export any table mapped in the
+:term:`app model`.  The only caveat is that it is "dumb" and does not
+have any special field handling.  This means the column headers in the
+CSV will be the same as in the source table, and some data types may
+not behave as expected etc.
+
+Defined in: :mod:`wuttasync.cli.export_csv`
+
+.. program-output:: wutta export-csv --help
+
+
 .. _wutta-import-csv:
 
 ``wutta import-csv``