Introduced input fields for "Title" and "Message" in the
EnvelopeSenderEditorPage, allowing users to specify metadata
for envelopes. The "Title" field is required and validated,
while the "Message" field is optional with a default value.
Updated the save logic to validate the title and display
appropriate error messages. Persisted the "Title" and
"Message" fields in the session cache via the
`EditorSessionData` record.
Modified the `CreateEnvelopeReceiverCommand` to use the
user-provided "Title" and "Message" values. Adjusted the UI
layout and styling to accommodate the new fields, ensuring
a seamless user experience.