refactor: renames schema to dto

i had been looking for a more appropriate name for the schema package
which holds our pyndatic models for marshalling and unmarshalling payloads
while models represent the persistent data models, schema was an ambigious
name for the function the pyndantic models bring to the app.

data transfer objects or dto is a much more appropriate name, thanks
@s3rius and the @taskiq-python project for springing this idea.

CLOSES #83

Author: devraj

README.md

@@ -118,7 +118,7 @@ Directory structure for our application:
  |   └─ routers/         -- FastAPI routers
  |   └─ tasks/           -- TaskIQ
  |   └─ models/          -- SQLAlchemy models
- |   └─ schema/          -- Pydantic schemas
+ |   └─ dto/             -- Data Transfer Objects
  |   └─ alembic/         -- Alembic migrations
  |   └─ __init__.py
  |   └─ api.py