Bring back describe sub-command

When you only have a single sub-command, `validate` in this case,
Typer seems to automatically move that functionality to the top-level
command. To get around that strangeness, I've re-added the `describe`
command that's intended to print out the file format and the validation
list, but isn't implemented yet. For now if you call it, it simply
reports _Feature coming soon..._

We'll implement this for real in a follow-up PR sometime soon.

regtech_data_validator/cli.py

@@ -36,6 +36,15 @@ class OutputFormat(StrEnum):
     TABLE = 'table'
 
 
+@app.command()
+def describe() -> None:
+    """
+    Describe CFPB data submission formats and validations
+    """
+
+    print('Feature coming soon...')
+
+
 @app.command(no_args_is_help=True)
 def validate(
     path: Annotated[
@@ -61,11 +70,9 @@ def validate(
     output: Annotated[Optional[OutputFormat], typer.Option()] = OutputFormat.TABLE,
 ):
     """
-    CFPB's RegTech data validation utility.
+    Validate CFPB data submission
     """
     context_dict = {x.key: x.value for x in context} if context else {}
-
-    # FIXME: Handle ParserError
     input_df = pd.read_csv(path, dtype=str, na_filter=False)
     is_valid, findings_df = validate_phases(input_df, context_dict)