Add ` uv run task emails` step to `DEVELOPMENT.md`?

[petrpavlik]

Just managed to run Polar locally based on DEVELOPMENT.md. Works great, I just had to run uv run task emails to make the db migration task succeed uv run task db_migrate. I mean the error log suggests to run it, but maybe it be worth explicitly mentioning it (or fixing it if this is not the intended behavior)

➜  server git:(main) ✗ uv run task db_migrate
Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "/Users/[censored]/Developer/polar/polar/server/scripts/db.py", line 8, in <module>
    from polar.config import settings
  File "/Users/[censored]/Developer/polar/polar/server/polar/config.py", line 296, in <module>
    settings = Settings()
               ^^^^^^^^^^
  File "/Users/[censored]/Developer/polar/polar/server/.venv/lib/python3.12/site-packages/pydantic_settings/main.py", line 176, in __init__
    super().__init__(
  File "/Users/[censored]/Developer/polar/polar/server/.venv/lib/python3.12/site-packages/pydantic/main.py", line 214, in __init__
    validated_self = self.__pydantic_validator__.validate_python(data, self_instance=self)
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
pydantic_core._pydantic_core.ValidationError: 1 validation error for Settings
EMAIL_RENDERER_BINARY_PATH
  Value error, 
        The provided email renderer binary path /Users/[censored]/Developer/polar/polar/server/emails/bin/react-email-pkg is not a valid file path
        or does not exist.

        If you're in local development, you should build the email renderer binary
        by running the following command:

        uv run task emails

         [type=value_error, input_value=PosixPath('/Users/[censored]...ls/bin/react-email-pkg'), input_type=PosixPath]
    For further information visit https://errors.pydantic.dev/2.10/v/value_error