Aligned with Homebrew formula

This is a test release aligned with https://github.com/zionlang/homebrew-zion

Install with brew install zionlang/zion/zion.

a little bit more stable

Version 0.3 includes support for global variable initialization. Currently only variables that are referenced within the dependency graph - starting at the program's main entry point - will be evaluated at program entry.

a relatively stable release

v0.2

bump version to 0.2