fix: use the lineWidth option for line breaking in flow collection

This should address issues eemeli#288 and eemeli#507.

src/stringify/stringifyCollection.ts

@@ -148,7 +148,7 @@ function stringifyFlowCollection(
  } else {
  if (!reqNewline) {
  const len = lines.reduce((sum, line) => sum + line.length + 2, 2)
- reqNewline = len > Collection.maxFlowStringSingleLineLength
+ reqNewline = (ctx.options.lineWidth != 0 && len > ctx.options.lineWidth)
  }
  if (reqNewline) {
  str = start