colnames should be optional in type definition for Alias

[markandrus]

Parsing SELECT * FROM t AS u produces a RangeVar for "t" with an Alias for "u". The type definition for Alias says colnames is required (although the comment says it is optional):

pg-parser/src/lib/ast.ts

Lines 4964 to 4969 in c613630

	export type Alias = {
	/** aliased rel name (never qualified) */
	aliasname: string
	/** optional list of column aliases */
	colnames: { String: String }[]
	}

The actual parse produces an Alias without colnames:

{
  "alias": {
    "aliasname": "u"
  }
}

I think the type should be updated as follows:

    /** aliased rel name (never qualified) */
    aliasname: string
    /** optional list of column aliases */
-   colnames: { String: String }[]
+   colnames?: { String: String }[]
  }

---

Parse SELECT * FROM t AS u with @pg-nano/parser

import { parseQuerySync } from '@pg-nano/pg-parser'

console.log(JSON.stringify(parseQuerySync('SELECT * FROM t AS u', null, 2))

/*

{
  "version": 160001,
  "stmts": [
    {
      "stmt": {
        "SelectStmt": {
          "targetList": [
            {
              "ResTarget": {
                "val": {
                  "ColumnRef": {
                    "fields": [
                      {
                        "A_Star": {}
                      }
                    ],
                    "location": 7
                  }
                },
                "location": 7
              }
            }
          ],
          "fromClause": [
            {
              "RangeVar": {
                "relname": "t",
                "inh": true,
                "relpersistence": "p",
                "alias": {
                  "aliasname": "u"
                },
                "location": 14
              }
            }
          ],
          "limitOption": "LIMIT_OPTION_DEFAULT",
          "op": "SETOP_NONE"
        }
      }
    }
  ]
}

*/