)
Returns the boolean value of the environment declaration name.
The boolean value of the declaration is true if the declared value is
the string "true", and false if the value is "false".
In all other cases, including when there is no declaration for name,
the result is the defaultValue.
Example:
const loggingFlag = const bool.fromEnvironment("logging");
If you want to use a different truth-string, you can use the
String.fromEnvironment constructor directly:
const isLoggingOn = (const String.fromEnvironment("logging") == "on");