fix(postgres): add py.typed marker to postgres module

[oliverlambson]

It's already fully typed, just not marked as such

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.05%. Comparing base (58459a1) to head (2eeb1ad).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@ Coverage Diff @@## main #849 +/- ##
=======================================
Coverage 83.05% 83.05% =======================================
Files 16 16 Lines 1700 1700 Branches 186 186 =======================================
Hits 1412 1412 Misses 234 234 Partials 54 54 

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[Tranquility2]

Not sure this is ready:
poetry run mypy --config-file pyproject.toml modules/postgres/testcontainers/postgres/

modules/postgres/testcontainers/postgres/__init__.py:48: error: Function is missing a type annotation for one or more arguments [no-untyped-def]
def __init__(
^
modules/postgres/testcontainers/postgres/__init__.py:60: error: Incompatible types in assignment (expression has type "Optional[str]", variable has type "str")
[assignment]
self.username: str = username or os.environ.get("POSTGRES_USER", "test")
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
modules/postgres/testcontainers/postgres/__init__.py:61: error: Incompatible types in assignment (expression has type "Optional[str]", variable has type "str")
[assignment]
self.password: str = password or os.environ.get("POSTGRES_PASSWORD", "test")
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
modules/postgres/testcontainers/postgres/__init__.py:62: error: Incompatible types in assignment (expression has type "Optional[str]", variable has type "str")
[assignment]
self.dbname: str = dbname or os.environ.get("POSTGRES_DB", "test")
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
modules/postgres/testcontainers/postgres/__init__.py:73: error: Incompatible default for argument "driver" (default has type "object", argument has type
"Optional[str]") [assignment]
def get_connection_url(self, host: Optional[str] = None, driver: Optional[str] = _UNSET) -> str:
^~~~~~
Found 5 errors in 1 file (checked 1 source file)

Maybe some stuff moved since this original commit?