Add meson build scripts

[gavr123456789]

Why not using meson?
Also first time see wren, it looks cool, I love smalltalk.

[cxw42]

I just discovered Wren recently as well, and it looks pretty nice.

Why not using meson?

No deep reason :) . I have not used Meson (and I'm writing my own build system ;) ).

I welcome a PR to add Meson! However, please do not remove Autotools. Thanks!