Add lint check or helper function for potential heading direction error

[xiashtra]

Feature(s) Requested

Add lint check to catch or helper function to prevent potential heading direction errors.

Ref: #752, #976

[xiashtra]

#752 (comment)

This code does look like it could produce an incorrect result, but the modulus operator in JavaScript does not constrain the result to a positive number.

const hdgTo16DirNum = 3;
console.log('Without abs: ' + (hdgTo16DirNum - 4) % 16);
console.log('With abs: ' + Math.abs((hdgTo16DirNum - 4) % 16));

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The fix here would be more like the following, I'd assume, but I don't have time to dig into the rest of the logic to determine if this is correct or not:

switch (matches.id) {
  case 'A45F':
    data.herosBlowSafeDir = ((Directions.hdgTo16DirNum(actor.Heading) - 4) + 16) % 16;
    break;
  case 'A461':
    data.herosBlowSafeDir = (Directions.hdgTo16DirNum(actor.Heading) + 4) % 16;
    break;
}

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This does seem like a potentially common problem to have happen, and we might want to see about adding linting to detect this or require the use of a helper method like Directions.mod16DirNum(start, by) that handles edge cases.