Games in a page

• New: a page can run JavaScript that draws on a <canvas>, with requestAnimationFrame, timers, the player's keys (W A S D, jump, sprint, Q, 1 to 9) and mouse, pictures, and mcgui.sound, mcgui.command and mcgui.player. Enough for Pong, Snake or a reaction test in one HTML file. See Scripts in the docs.
• mcgui.command runs only from the player's own click or key press, never as a page opens or from a timer, so a page cannot run commands as whoever opens it.
• Scripts never run on the server's main thread, each player gets their own copy, and a frame that runs longer than 250 ms stops the script. Errors go to the console with the page and line.
• Newer JavaScript (class, ... spread, async and await) is converted the first time a page opens.
• The script engine is not in the jar, which stays small: MC GUI fetches it from cdn.resourcepack.ai (2.4 MB, once) the first time a page with a script opens, checks it is the exact file this version was built with, and keeps it in plugins/MCGUI/libs/. A server without internet can put MCGUI-scripts-0.6.2.jar there by hand.
• Pages without a script work exactly as before, and a server that never shows one never fetches anything.