docs(bigquery): update package docs to show query parameterization (#…

…8965)

Improve discoverability of parameterization by making it part of the
package level docs.

We also cleanup the backtick in the table reference as BQ no longer
requires literal escaping for project identifiers.

bigquery/doc.go

@@ -33,15 +33,19 @@ To start working with this package, create a client:
 
 # Querying
 
-To query existing tables, create a Query and call its Read method:
+To query existing tables, create a Query and call its Read method, which starts the
+query and waits for it to complete:
 
 	q := client.Query(`
 	    SELECT year, SUM(number) as num
-	    FROM ` + "`bigquery-public-data.usa_names.usa_1910_2013`" + `
-	    WHERE name = "William"
+	    FROM bigquery-public-data.usa_names.usa_1910_2013
+	    WHERE name = @name
 	    GROUP BY year
 	    ORDER BY year
 	`)
+	q.Parameters = []bigquery.QueryParameter{
+		{Name: "name", Value: "William"},
+	}
 	it, err := q.Read(ctx)
 	if err != nil {
 	    // TODO: Handle error.