psql include text file with bom

*Summary:*

psql "include" or "\i" command chokes on UTF8 text files prefixed with BOM.

*Steps to reproduce:*

1. create a UTF8 file with three byte BOM 'EF BB BF'.
2. include the file from psql via the "include" or \i command.

Example output for file named "test.sql" below:

redacted-# \i test.sql
psql:test.sql:1: ERROR:  syntax error at or near ""
LINE 1: 

*Background*

https://en.wikipedia.org/wiki/Byte_order_mark

Some text editors save text to a file prefixed by a BOM or byte marker.
This includes Visual Studio, VSCode and others.

I think it would be reasonable for the include command to skip over any
BOM found in the first two or three bytes of a file.