Support numbers in Join type

[o-alexandrov]

Thank you for the Join type, really helpful.
Let's please support number parameters as well, so we could create results like the one below:

• foo.0.bar

On a side note, I'm using Join type to cast type override on Array.join() and this native JavaScript function supports number parameters, which leads to believe this Join type should support it too.

[o-alexandrov]

@avaly hello, sorry for the ping, you might want to comment on it, since Join type is your addition

[sindresorhus]

Can you update the doc comment to indicate that it accepts numbers too?

[o-alexandrov]

@sindresorhus thank you for taking time and I apologize for forgetting to update some of the related docs.
in the last commit above, I carefully reviewed missed docs comments and updated them.