templates: add __init__.py files to templates/ dirs...
templates: add __init__.py files to templates/ dirs
This is necessary for them to be loaded with `importlib.resources`,
which we want to do for PyOxidizer and similar. `importlib.resources`
cannot read resources from submodules
(`resources.open_binary('mercurial.templates', 'coal/map')` is not
valid), so we need one `__init__.py` per directory.
Differential Revision:
https://phab.mercurial-scm.org/D8854