add Snowflake dialect.

[igalklebanov]

Hey 👋

snowflake-sdk has been growing, and now sits at 1M~ downloads per week on NPM.

The issue with these stats is they don't show usage in (modern) TypeScript projects in particular or whether there's enough interest for a Kysely dialect. There's a @types/snowflake-sdk that gets downloaded 300-400k times per week, and is on a natural decline given that snowflake-sdk now ships dts files.

React to this issue's main post with a 👍 or something to let us know you're interested in a dialect.