want an extension which can read line and can edit line an online file

I want an extension which can edit and read online file 
please make an extention with only two blocks like this
but please note that it can read or edit file which are uploded online For Example :- www.xyz.com/file.txt
filepath = "www.xyz.com/file.txt"
x = File.ReadLine(filePath, lineNumber)
File.WriteLine(filePath, lineNumber, contents)

I want so many things. Most things I want need to be paid for.

If you are looking for advice how to do it by yourself : learn server side scripting

You can't do what you want if you don't control the server-side. Be it a docker, vm or private server.
You could run things from your local computer(s) but you need administrative access on your router.
And of course the computer you run, as a server, should be on all the time you want to run the service for your game.

If you want someone to make this you propably should provide more information,
because I estimate that you are only looking at a solution that MIGHT work for your idea. Depending on the reason you
need this there are propably much better solutions than a textfile that only one game at a time can access.

You can also run some examples from my extension list. Maybe something that is there will help you:
http://photoquesting.com/repo/

I learn server side scripting i.e php , e.t.c    and make leaderboard 
using get and post request FREE bro