add more machine-readable data about the license
add more machine-readable data about the license

This small change is meant to make LibreJS happy.

Closes: #1273

handlebars-lang/handlebars.js,mosoft521/handlebars.js,gautamkrishnar/handlebars.js,jbboehr/handlebars.js,jbboehr/handlebars.js,mosoft521/handlebars.js,wycats/handlebars.js,jbboehr/handlebars.js,wycats/handlebars.js,handlebars-lang/handlebars.js,handlebars-lang/handlebars.js,handlebars-lang/handlebars.js,wycats/handlebars.js,gautamkrishnar/handlebars.js,handlebars-lang/handlebars.js,wycats/handlebars.js,gautamkrishnar/handlebars.js,mosoft521/handlebars.js,mosoft521/handlebars.js,wycats/handlebars.js,mosoft521/handlebars.js