Add helpers functions to sql(db)

[lucleray]

const sql = require('@sequencework/sql/pg')

// main method stays the same
const query = sql`select * from movies where id = ${id}` 

// default pg result object : https://node-postgres.com/api/result
const { rows, rowCount } = await sql.query(db)`select * from movies` 

// helpers
const movies = await sql.many(db)`select * from movies`
const movie = await sql.one(db)`select * from movies where id = ${id}`
const nbMovie = await sql.count(db)`update from movies set name = ${name} where id = ${id}`

[yannvgn]

Let's merge that!

[yannvgn]

wait, readme has to be updated