Create examples for every function of HashSet

[nikgraf]

https://github.com/reason-association/reasonml.org/blob/master/pages/belt_docs/hash-set.mdx

[tgrecojs]

Going to try & help out with this at #70.

[tgrecojs]

https://github.com/reason-association/reasonml.org/blob/master/pages/belt_docs/hash-set.mdx

I think the URLs must have either changed or maybe is it an access problem? Seems like this should point to https://github.com/reason-association/reasonml.org/blob/master/pages/apis/javascript/latest/belt/hash-set.mdx but could be wrong.

[ryyppy]

that's a correct assumption, this is a rather old issue