add README

README.md

+# Lovebyte 2021 seminars
+
+Seminars given at the Lovebyte 2021 online demoparty, each 256 seconds (or
+less) in length, teaching you how to get started with sizecoding on several
+platforms.
+
+* `dmg-cgb`: Gameboy, Gameboy Color
+* `gba`: Gameboy Advance
+* `gcn`: Gamecube
+* `linux`: Linux
+* `snes`: SNES
+* `ti8xz80`: TI-8x (Z80 and eZ80)
+
+Run `make` to generate the PDFs of all the presentations, from their LaTeX
+beamer sources.