Allow stdin and piping as input

[nkakouros]

I have a tool that outputs some markdown. I would like to pipe that markdown to markcat so that it is beautifully rendered. But I couldn't do that.

mytool | markcat

results in an error:

File doesn't exist

and an exit code of 1.

I also tried to use markcat <<< "$(mytool)" but that failed in a similar way.

[BubuAnabelas]

That's because currently markcat only supports reading from files.

I'll change the title of the issue and make it a requested feature, you can contribute by changing this file and making a pull request if you wish.