Add '+' or '*' register to yank/paste from system clipboard.

[asford]

In vim-like bindings the * and/or + registers target yank/paste operations to/from the system clipboard.

This is a very useful form of interop and is, for example, implemented in CodeMirror-vim via (replit/codemirror-vim#29) and (replit/codemirror-vim#36).

Would you be open to a patch adding the + or * registers to monaco-vim?