Add possibility to choose line-length for erlfmt

[PhysicistProgs]

Formatter erlfmt has feature to choose line-length.
We need possibility to add setting to vscode settings, something like that:

"erlangFormatter.args": ["--print-width", "120"],

[PhysicistProgs]

It is quite easy fix, I can do it myself if you'd like it.

I make it work locally but fix is quite ugly and doesn't include correctness check.
How it looks now:

function formatterArgs(outputChannel) {
    const config = vscode_1.workspace.getConfiguration("erlangFormatter");
    const formatter = config.get("formatter");
    
    const args = config.get("args");
    outputChannel.appendLine(`args: ${args.join(" ")}`);
    outputChannel.appendLine(`args: ${args}, ${formatterCommand(formatter)}`);

    switch (formatter) {
        case "rebar3_format":
            return [formatterCommand(formatter), "--files"].concat(args);
        case "steamroller":
            return [formatterCommand(formatter), "-f"].concat(args);
        case "erlfmt":
            return [formatterCommand(formatter), "-w"].concat(args);
        default:
            throw new Error(`Error while reading Erlang formatter configuration: ${formatter}`);

I can change it due to your requirements.

[szTheory]

Cool! Please open a PR

[PhysicistProgs]

Opened PR: #13