Enable passing terser options with rails directly to Terser::Compressor

[javier-menendez]

Purpose

Add a way to pass options to the terser compressor when using rails.

Existing way:

config.assets.js_compressor = Terser.new(compress: { drop_console: true })

The problem with this way of passing options is that bypasses the Terser::Compressor class and uses directly Terser#compile since there is an alias for compress

Proposed new way:

config.assets.js_compressor = :terser
config.assets.terser = { compress: { drop_console: true } }

This way the Terser::Compressor is going to be used with their call methods according to the Sprockets version

[ahorek]

thanks!