feat: Add charset custom

[dliocode]

No description provided.

[dliocode]

`Why use:

const config = {
host: '127.0.0.1',
port: 3050,
database: "/path/to/base.fdb",
user: "SYSDBA",
password: "masterkey",
lowercase_keys: true,
pageSize: 4096,
retryConnectionInterval: 1000,
encoding: 'WIN1252',
charset: 'latin1' // Add new configuration - charset custom
}
`

[nickolasdeluca]

This is a neat feature that has been requested by the south american comunity, would be great to be able to stop modifying the source code of the package on production environments.