Support for ansible vault content

[Knskan3]

At the moment when trying to read a yaml file with ansible vault values, it will throw an exception
YAMLException: unknown tag !<!vault>

https://docs.ansible.com/ansible/latest/user_guide/vault.html#ansible-vault

Thanks

[puzrin]

Custom tags shold be implemened at user side, here is nothing to add. Ignoring nimplemed ags will be possible when #385 done.

[bignose-debian]

Custom tags shold be implemened at user side, here is nothing to add.

At the 'js-yaml' project there appears to be no clear guidance how the "user side" should do this. Can you reply here and link to comprehensive documentation for how to do this for 'js-yaml', so people who find this issue can implement custom tags as you say?