Add welcome/description text

[toivoh]

It would be nice if you would add some text to the user interface to explain a little bit about what VGA Playground is and what you can do with it/how to use it.
It could for example say something like

• Here you can write Verilog code that generates VGA output and see the results
• Describe the VGA interface: recommended Tiny VGA pinout for Tiny Tapeout?
• Point to the utility code that is included (e g the hvsync generator, hopefully with a bit of documentation)
• Note that the code could be compiled for FPGA or ASIC?
• Note that it uses Verilator to run on your PC?