Fixing the use of Ghostscript gs command

[0nyr]

This PR is linked to the following issue: Issue 67

I just moved all code that was building a gs command into a dedicated function that checks if the gs command is available in the shell, else defaults to use Ghostscript_jll.

This allows to fix the issue on Nixos.

[tecosaur]

Just commenting on one small part of this: I believe Sys.which exists.

[0nyr]

Just commenting on one small part of this: I believe Sys.which exists.

Yes, just stumble across it yesterday when trying to dig in my low-resolution latex issue. I also discovered const Ref which will be much better for the variable checking the availability of gs. I'll make a new commit today with those improvements.

I'm still quite new to Julia.

[asinghvi17]

Thanks for the PR, will look into this and the rendering issue in more detail tomorrow. Are you still intending to make another commit, or should I review it as is?

[0nyr]

Thanks for the PR, will look into this and the rendering issue in more detail tomorrow. Are you still intending to make another commit, or should I review it as is?

Sorry, working on another stuff, but I will commit to improve asap. Thanks.

[0nyr]

@asinghvi17 So here we are. I added a flake to work with Nix. Also made a proper dir for example files from the README.md to help contributors and users alike to get a feeling of how to use MakieTeX.jl and added the check for Ghostscript with the other top-level variables.

Tested successfully on my machine.

I must mention that I still have the "pixelated" rendering issue, which is unrelated with the Ghostscript dynamically linked executables issue 67.