When true, a path in ConfigPluginOptions.envFilePath that
does not exist is skipped instead of throwing. Defaults to false, which
is the behaviour released in 0.1.0.
This exists for the layered-dotenv arrangement a scaffolded project uses: a
gitignored .env beside a tracked .env.example. The file is present on
the machine that generated it and absent on every fresh clone, in CI, and
in a container built from the repository — so requiring it would make the
project fail to start everywhere except its author's machine. A file that
EXISTS but cannot be read still throws; only absence is tolerated.
Ignored when ConfigPluginOptions.instance is set.