Add missing libraries.properties

[AdamDemirel]

Hi there, thanks for this library.

I just wanted to let you know that an error will now be encountered uploading this zip as a custom library without a library.properties file with the following metadata: https://arduino.github.io/arduino-cli/library-specification/#libraryproperties-file-format

Without it, the error [] library.properties not found is thrown

A minimal viable fix is a library.properties file with roughly the following:

name=Artnet-Master
version=1.0.0
author=Cristian Maglie <c.maglie@example.com>, Pippo Pluto <pippo@example.com>
maintainer=Cristian Maglie <c.maglie@example.com>
sentence=A library that makes coding a Webserver a breeze.
paragraph=Supports HTTP1.1 and you can do GET and POST.
category=Communication
url=http://example.com/
architectures=avr
includes=WebServer.h
depends=ArduinoHttpClient