v0.1-alpha: Screenshots in README.md

Ready-to-use disk images for TRS-80 Model 4/4p UCSD Pascal from Softech.

• ucsd-st: FreHD image for UCSD Pascal (Qwerty);
• ucsdstfr: FreHD image for UCSD Pascal (Azerty);
• *.HFE files: Disk images for HxC-2001 Floppy Emulator;
• *.JV3 files: Disk images for various TRS-80 emulators.