feat(endo): Improve JSON file parse error messages

[kriskowal]

This change annotates JSON syntax errors with the location of the originating file throughout Endo.

[erights]

Suggested change

	throw new SyntaxError(`Cannot parse JSON from ${location}, ${error}`);
	if (error instanceof SyntaxError) {
	throw new SyntaxError(`Cannot parse JSON from ${location}, ${error}`);
	} else {
	throw error;
	}

See also my comments in #431 about whether the following approach might be better:

Suggested change

	throw new SyntaxError(`Cannot parse JSON from ${location}, ${error}`);
	if (someAppropriateOption) {
	console.log(`Cannot parse JSON from ${location},`, error);
	}
	throw error;

[warner]

looks good to me