keyboard/altgr: msx code layout

Example of better times (my first computer before Windows dark ages).
Characters manually transcribed from printed 1984 Toshiba HX-10 owner's
manual (figure 3.2.5-6 When [CODE] key is pressed).

Cover image modified from a nice image of such an HX-10 with graph stickers:
https://www.nightfallcrew.com/wp-content/gallery/toshiba-hx-10-64k-msx-keyboard-fix/20151210_235257.jpg