NETSCRIPT: Added changing tail font size through scripts

[G4mingJon4s]

It is now possible to change the font size for each tail window through the API. The font size is stored on the RunningScript, also giving access to the current font size value through ns.self and other API functions.

This adds another function to the general netscript functions. Since there are a lot of tail specific functions, it would make sense to move them to their own interface. If this is desired, I would be more than happy to move them in this PR.

Test code:

export async function main(ns: NS) {
  ns.disableLog("ALL");
  ns.clearLog();
  ns.tail();

  ns.print("Test string");
  ns.print("Multi\nLine\nStuff");

  while (true) {
    await ns.asleep(1000);
    ns.setTailFontSize(); // omitting resets the font size to the default, set in the style editor

    await ns.asleep(1000);
    ns.setTailFontSize(20);

    await ns.asleep(1000);
    ns.setTailFontSize(16);

    await ns.asleep(1000);
    ns.setTailFontSize(12);
  }
}