Export dptlib

[evekto]

This PR has 2 goals:

• Remove dynamic imports so it's easier to integrate this lib into bundler-setups
• Export dptlib so that binary KNX data can be encoded and decoded directly with buffers

Changes to the code are kept to a minimun, so that usage may not be very convenient but it works:

import { dptlib } from "knx";

const subtype = dptlib.DPT5.subtypes['001'];
const value = dptlib.fromBuffer(Buffer.from([0xff]), dptlib.DPT5, subtype)
console.log('decoded:', value, subtype.unit);

const apdu = {};
dptlib.populateAPDU(100, apdu, "DPT5.001")
console.log('encoded:', apdu.data);