alembic init with pyproject template, and existing pyproject.toml, does not have a newline

[jvanasco]

Given an existing pyproject.toml:

[tool.black]
target-version = ['py37']

[tool.mypy]
python_version = "3.10"

The alembic command::

alembic init --template pyproject alembic

Modifies the file to contain::

[tool.black]
target-version = ['py37']

[tool.mypy]
python_version = "3.10"[tool.alembic]

# path to migration scripts.

Note the lack of newline(s) before [tool.alembic]. Ideally there should be 2.

[jvanasco]

I proposed a quick fix for this in #1680 by adding an "append_delimiter" kwarg.

[sqla-tester]

jonathan vanasco has proposed a fix for this issue in the main branch:

support 'append_delimiter' to fix #1679 https://gerrit.sqlalchemy.org/c/sqlalchemy/alembic/+/5989