Make default command accept same args as 'add' command

Now 'blurb -i 123' works the same as 'blurb add -i 123', because nobody
expects the Spanish Inquisition... or having to type 'add' every time.

- Forward all add command parameters to the default command
- Update help text to indicate 'add' is the default command
- Parameters like --issue, --section, and --rst-on-stdin now work
  directly with 'blurb' without specifying 'add'

Author: gpshead

src/blurb/blurb.py

@@ -912,10 +912,11 @@ def add(*, issue: Annotated[Optional[str], Parameter(alias=["-i"])] = None,
         section: Annotated[Optional[str], Parameter(alias=["-s"])] = None,
         rst_on_stdin: bool = False):
     # This docstring template is formatted after the function definition.
-    """Add a new Misc/NEWS entry.
+    """Add a new Misc/NEWS entry (default command).
 
     Opens an editor to create a new entry for Misc/NEWS unless all
-    automation parameters are provided.
+    automation parameters are provided. This is the default command when
+    no subcommand is specified.
 
     Use -i/--issue to specify a GitHub issue number or link.
     Use -s/--section to specify the NEWS section (case insensitive with partial matching).
@@ -1223,9 +1224,11 @@ def export():
 
 
 @app.default
-def default_command():
+def default_command(*, issue: Annotated[Optional[str], Parameter(alias=["-i"])] = None,
+                   section: Annotated[Optional[str], Parameter(alias=["-s"])] = None,
+                   rst_on_stdin: bool = False):
     """Default to 'add' command when no subcommand specified."""
-    add()
+    add(issue=issue, section=section, rst_on_stdin=rst_on_stdin)
 
 
 def main():