Add support for sqlc.slice()

[daison12006013]

I've noticed that when using sqlc.slice('names'), it really behaves differently, compared to what it is generated in golang

Expectation:

• it should make the names as array like data once it's converted to typescript

Outcome:

• it converts to string | null type only!

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in Golang, it is correctly converted and the logic that replaces the docblock SQL Slice is being written properly

In typescript, it is wrongly interpreted, basically mysql2 requires to be an array so that it will do its job to wrap it into a comma separated values.