Homebrew formula for Metanorma

Allows installing Metanorma using Homebrew package manager on macOS.

• Formula

To install, run:

brew tap metanorma/metanorma
brew install metanorma

Alternatively:

brew install metanorma/metanorma/metanorma

Or

brew install --HEAD https://raw.githubusercontent.com/metanorma/homebrew-metanorma/master/metanorma.rb