Add a new createNode option aliasDuplicateObjects

[eemeli]

Fixes #296, originally reported in #211

This adds an option aliasDuplicateObjects (default true) that does this:

const foo = { foo: 'FOO' }

const doc1 = new YAML.Document([foo, foo])
const doc2 = new YAML.Document([foo, foo], { aliasDuplicateObjects: false })

`${doc1}
---
${doc2}`

- &a1
  foo: FOO
- *a1

---
- foo: FOO
- foo: FOO

Ping @ChocolateLoverRaj, @ushuz, @dudif91. This would presumably work for you?

[ushuz]

Thank you for addressing #211

[ushuz]

aliasDupplicateObjects feels too implementation-focus. I would prefer something like anchors proposed by #211, which will sit well with anchorPrefix below and is easier for users to understand IMO.

[ChocolateLoverRaj]

@eemeli whatever the option is called, it works for me.

[derolf]

When will it be released?

[eemeli]

@derolf https://github.com/eemeli/yaml/releases/tag/v2.0.0-8