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

This should address issues #288 and #507.

Author: no92

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

tests/doc/stringify.ts

@@ -616,7 +616,7 @@ describe('scalar styles', () => {
   y,
   n
 ]\n`
-    expect(String(doc)).toBe(str)
+    expect(doc.toString({ lineWidth: 1 })).toBe(str)
     expect(YAML.parse(str)).toEqual([
       true,
       false,