As original TinyBasicPlus implementation doesn't support STRING variables,

I started a little-experimental support for those.

I added 4 string vars. $1 to $4 (I know : it's not the casual formalism for BASIC string values, but it was simplier to modify the interpreter by this way... maybe later, will do better)

So I can now transform my little board into a notepad, typewriter.. or simply displays what user inputs...

(GitHub is up to date...)