code: function findAtDecl (decls, prop) {
    const foundDecls = decls.filter((decl) => {
      return (isPlainObject(decl) &&
            Object.keys(decl).length > 0 &&
            Object.keys(decl)[0] === `@${prop}`) || decl === `@${prop}`
    })
  
    if (foundDecls.length === 0) { return }
  
    const decl = foundDecls[0]
  
    return isPlainObject(decl) ? Object.values(decl)[0] : true
  }
docs: finds the given at declaration value
  @param  {Array[Object]} decls the decls from an element
  @param  {String}        the prop
  @return {Any}           the found value